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1 | Term | Definition | Source | Comments | ||||||||||||||||||||||
2 | abbreviation abbreviations | shortened form of a word, phrase, or name where the abbreviation has not become part of the language This includes initialisms and acronyms where: initialisms are shortened forms of a name or phrase made from the initial letters of words or syllables contained in that name or phrase Not defined in all languages. SNCF is a French initialism that contains the initial letters of the Société Nationale des Chemins de Fer, the French national railroad. ESP is an initialism for extrasensory perception. acronyms are abbreviated forms made from the initial letters or parts of other words (in a name or phrase) which may be pronounced as a word NOAA is an acronym made from the initial letters of the National Oceanic and Atmospheric Administration in the United States. Some companies have adopted what used to be an initialism as their company name. In these cases, the new name of the company is the letters (for example, Ecma) and the word is no longer considered an abbreviation. | wcag-2 | |||||||||||||||||||||||
3 | Accessibility API accessibility api accessibility apis | Operating systems and other platforms provide a set of interfaces that expose information about objects and events to assistive technologies. Assistive technologies use these interfaces to get information about and interact with those widgets. Examples of accessibility APIs are Microsoft Active Accessibility [[MSAA]], Microsoft User Interface Automation [[UI-AUTOMATION]], MSAA with UIA Express [[UIA-EXPRESS]], the Mac OS X Accessibility Protocol [[AXAPI]], the Linux/Unix Accessibility Toolkit [[ATK]] and Assistive Technology Service Provider Interface [[AT-SPI]], and IAccessible2 [[IAccessible2]]. | aria-common | |||||||||||||||||||||||
4 | accessibility information (WCAG) | Information that web content must contain in order to meet a WCAG 2.0 success criterion (Level A, AA or AAA). Examples include: programmatically associated alternative content (e.g. text alternatives for images), role, and state information for widgets, relationships within complex tables). Note: For the purposes of ATAG 2.0, only programmatically determinable accessibility information qualifies. For additional examples, see Appendix A of the Implementing ATAG 2.0 document. | atag-2 | |||||||||||||||||||||||
5 | accessibility problems | ATAG 2.0 recognizes two types of accessibility problems: authoring tool user interface accessibility problems: Aspects of an authoring tool user interface that does not meet a success criterion in Part A of ATAG 2.0. web content accessibility problems (WCAG): Aspects of web content that does not meet a WCAG 2.0 success criterion (Level A, AA or AAA). | atag-2 | |||||||||||||||||||||||
6 | Accessibility Subtree | An accessible object in the accessibility tree and its descendants in that tree. It does not include objects which have relationships other than parent-child in that tree. For example, it does not include objects linked via aria-flowto unless those objects are also descendants in the accessibility tree. | aria-common | |||||||||||||||||||||||
7 | accessibility supported accessibility-supported accessibility support | supported by users' assistive technologies as well as the accessibility features in browsers and other user agents To qualify as an accessibility-supported use of a Web content technology (or feature of a technology), both 1 and 2 must be satisfied for a Web content technology (or feature): The way that the Web content technology is used must be supported by users' assistive technology (AT). This means that the way that the technology is used has been tested for interoperability with users' assistive technology in the human language(s) of the content, AND The Web content technology must have accessibility-supported user agents that are available to users. This means that at least one of the following four statements is true: The technology is supported natively in widely-distributed user agents that are also accessibility supported (such as HTML and CSS); OR The technology is supported in a widely-distributed plug-in that is also accessibility supported; OR The content is available in a closed environment, such as a university or corporate network, where the user agent required by the technology and used by the organization is also accessibility supported; OR The user agent(s) that support the technology are accessibility supported and are available for download or purchase in a way that: does not cost a person with a disability any more than a person without a disability and is as easy to find and obtain for a person with a disability as it is for a person without disabilities. The Accessibility Guidelines Working Group and the W3C do not specify which or how much support by assistive technologies there must be for a particular use of a Web technology in order for it to be classified as accessibility supported. (See Level of Assistive Technology Support Needed for "Accessibility Support".) Web technologies can be used in ways that are not accessibility supported as long as they are not relied upon and the page as a whole meets the conformance requirements, including Conformance Criterion 4 and Conformance Criterion 5, are met. When a Web Technology is used in a way that is "accessibility supported," it does not imply that the entire technology or all uses of the technology are supported. Most technologies, including HTML, lack support for at least one feature or use. Pages conform to WCAG only if the uses of the technology that are accessibility supported can be relied upon to meet WCAG requirements. When citing Web content technologies that have multiple versions, the version(s) supported should be specified. One way for authors to locate uses of a technology that are accessibility supported would be to consult compilations of uses that are documented to be accessibility supported. (See Understanding Accessibility-Supported Web Technology Uses.) Authors, companies, technology vendors, or others may document accessibility-supported ways of using Web content technologies. However, all ways of using technologies in the documentation would need to meet the definition of accessibility-supported Web content technologies above. | wcag-2 | |||||||||||||||||||||||
8 | Accessibility Tree | Tree of accessible objects that represents the structure of the user interface (UI). Each node in the accessibility tree represents an element in the UI as exposed through the accessibility API ; for example, a push button, a check box, or container. | aria-common | |||||||||||||||||||||||
9 | accessible content support features | Any features of an authoring tool that directly support authors in increasing the accessibility of the web content being edited. These are features that must be present to meet the success criteria in Part B of ATAG 2.0. | atag-2 | |||||||||||||||||||||||
10 | Accessible Description | An accessible description provides additional information, related to an interface element, that complements the accessible name. The accessible description might or might not be visually perceivable. | aria-common | |||||||||||||||||||||||
11 | Accessible Name | The accessible name is the programmatically determined name of a user interface element that is included in the accessibility tree. The accessible name is calculated using the accessible name and description computation. For native markup languages, such as HTML and SVG, additional information on how to calculate the accessible name can be found in HTML Accessibility API Mappings 1.0, Accessible Name and Description Computation (working draft) and SVG Accessibility API Mappings, Name and Description (working draft). For more details, see examples of accessible name. Note: As per the accessible name and description computation, each element always has an accessible name. When no accessible name is provided, the element will nonetheless be assigned an empty ("") one. Note: As per the accessible name and description computation, accessible names are flat string trimmed of leading and trailing whitespace. Notably, it is not possible for a non-empty accessible name to be composed only of whitespace since these must be trimmed. Accessibility Support for Accessible Name Because the accessible name and description computation is not clear about which whitespace are considered, browsers behave differently when trimming and flattening the accessible name. For example, some browsers completely trim non-breaking spaces while some keep them in the accessible name. There exists a popular browser which does not perform the same trimming and flattening depending whether the accessible name comes from content, an aria-label attribute, or an alt attribute. There exists a popular browser which assign no accessible name (null) when none is provided, instead of assigned an empty accessible name (""). The accessible name and description computation suggest that if an aria-labelledby attribute refers to an existing but empty element, the computation should stop and return an empty name without defaulting to the next steps. Several user agents and assistive technologies chose to use the next step in the computation in this case. | act-rules | |||||||||||||||||||||||
12 | Accessible Name accessible name accessible names | The accessible name is the name of a user interface element. Each platform accessibility API provides the accessible name property. The value of the accessible name may be derived from a visible (e.g., the visible text on a button) or invisible (e.g., the text alternative that describes an icon) property of the user interface element. See related accessible description. A simple use for the accessible name property may be illustrated by an "OK" button. The text "OK" is the accessible name. When the button receives focus, assistive technologies may concatenate the platform's role description with the accessible name. For example, a screen reader may speak "push-button OK" or "OK button". The order of concatenation and specifics of the role description (e.g., "button", "push-button", "clickable button") are determined by platform accessibility APIs or assistive technologies. | aria-common | |||||||||||||||||||||||
13 | Accessible object accessible object accessible objects | A node in the accessibility tree of a platform accessibility API . Accessible objects expose various states, properties, and events for use by assistive technologies. In the context of markup languages (e.g., HTML and SVG) in general, and of WAI-ARIA in particular, markup elements and their attributes are represented as accessible objects. | aria-common | |||||||||||||||||||||||
14 | activate | To carry out the behaviors associated with an enabled element in the rendered content or a component of the UA user interface. | uaag-2 | |||||||||||||||||||||||
15 | Activation behavior | The action taken when an event, typically initiated by users through an input device, causes an element to fulfill a defined role. The role may be defined for that element by the host language, or by author-defined variables, or both. The role for any given element may be a generic action, or may be unique to that element. For example, the activation behavior of an HTML or SVG <a> element shall be to cause the user agent to traverse the link specified in the href attribute, with the further optional parameter of specifying the browsing context for the traversal (such as the current window or tab, a named window, or a new window); the activation behavior of an HTML <input> element with the type attribute value submit shall be to send the values of the form elements to an author-defined IRI by the author-defined HTTP method. | aria-common | |||||||||||||||||||||||
16 | Adjectival rating Adjective-based Adjectival Adjectival rating | A system to report evaluation results as a set of human-understandable adjectives which represent groupings of scores. | wcag-3 | |||||||||||||||||||||||
17 | Age Related Forgetfulness Age Appropriate Forgetfulness age-related forgetfulness | Sometimes called "Age Appropriate Forgetfulness" or "Age Related Memory Loss". People with age related forgefulness have impaired memory issues that can be a normal part of healthy aging. They may take longer to learn new things, forget something but remember it later, or occasionally forget particular words. (This differs from dementia where forgetfulness is due to a disorder and is more pronounced.) | content-usable | |||||||||||||||||||||||
18 | AI | Artificial Intelligence | captcha | |||||||||||||||||||||||
19 | Alternative and Augmentative Communication System AAC | Sometimes called “AAC”. Any method, device, or application that can be used to help those who cannot use spoken language and need additional support by means of symbols, images, and/or text. For example, a screen with symbols that the user can select to speak the appropriate words or add them to a document. | content-usable | |||||||||||||||||||||||
20 | alternative content | Web content that user agents can programmatically determine is usable in place of other content that some people are not able to access. Alternative content fulfills essentially the same function or purpose as the original content. There are several general types of alternative content: text alternative for non-text content: Text that is programmatically associated with non-text content or referred to from text that is programmatically associated with non-text content. For example, an image of a chart might have two text alternatives: a short text alternative and a described-by relationship to a nearby paragraph that more fully describes the content of the chart. alternative for time-based media: Web content that serves the same function or purpose as one or more tracks in a time-based media presentation. This includes alternatives for audio such as captions and sign language interpretation, and alternatives for video such as audio descriptions and extended audio descriptions. Another form of time-based media alternative is a correctly sequenced text description of time-based visual and auditory information that also is capable of achieving the outcomes of any interactivity in the time-based presentation. text alternatives for text content: Text that is programmatically associated with certain types of text content to provide expanded information. For example, an abbreviation (or acronym) can provide an expansion of the shortened word or initialized words (<abbr title="User Agent Accessibility Guidelines">UAAG</abbr>). media alternative for text: Media that presents no more information than is already presented in text (directly or via text alternatives). A media alternative for text is provided for people who benefit from alternate representations of text. Media alternatives for text can be audio-only, video-only (including sign-language video), or audio-video. Note: According to WCAG 2.0, alternative content may or may not be programmatically determinable (e.g., a short description for an image might appear in the image's description attribute or within text near the image). However, UAAG 2.0 adds the programmatically available condition because this is the only type of alternative content that user agents can recognize. | uaag-2 | |||||||||||||||||||||||
21 | alternative content | Web content that is used in place of other content that some people are not able to access. Alternative content fulfills essentially the same function or purpose as the original content. WCAG 2.0 recognizes several general types of alternative content: text alternatives for non-text content: Text that is programmatically associated with non-text content or referred to from text that is programmatically associated with non-text content. For example, an image of a chart might have two text alternatives: a description in the paragraph after the chart and a short text alternative for the chart indicating in words that a description follows. alternatives for time-based media: Web content that serves the same function or purpose as one or more tracks in a time-based media presentation. This includes: captions, audio descriptions, extended audio descriptions, sign language interpretation as well as correctly sequenced text descriptions of time-based visual and auditory information that also is capable of achieving the outcomes of any interactivity in the time-based presentation. media alternative for text: Media that presents no more information than is already presented in text (directly or via text alternatives). A media alternative for text is provided for people who benefit from alternate representations of text. Media alternatives for text may be audio-only, video-only (including sign-language video), or audio-video. Importantly, from the perspective of authoring tools, alternative content may or may not be: programmatically associated alternative content: Alternative content whose location and purpose can be programmatically determined from the original content for which it is serving as an alternative. For example, a paragraph might serve as a text alternative for an image, but it is only programmatically associated if this relationship is properly encoded (e.g. by "aria-labeledby"). Note: ATAG 2.0 typically refers to programmatically associated alternative content. | atag-2 | |||||||||||||||||||||||
22 | alternative for time-based media | document including correctly sequenced text descriptions of time-based visual and auditory information and providing a means for achieving the outcomes of any time-based interaction A screenplay used to create the synchronized media content would meet this definition only if it was corrected to accurately represent the final synchronized media after editing. | wcag-2 | |||||||||||||||||||||||
23 | alternative text | Text that is associated with, and provides a brief description or label of, non-text content. | captcha | |||||||||||||||||||||||
24 | ambiguous to users in general | the purpose cannot be determined from the link and all information of the Web page presented to the user simultaneously with the link (i.e., readers without disabilities would not know what a link would do until they activated it) The word guava in the following sentence "One of the notable exports is guava" is a link. The link could lead to a definition of guava, a chart listing the quantity of guava exported or a photograph of people harvesting guava. Until the link is activated, all readers are unsure and the person with a disability is not at any disadvantage. | wcag-2 | |||||||||||||||||||||||
25 | animation | Graphical content rendered to automatically change over time, giving the user a visual perception of movement. Examples include video, animated images, scrolling text, programmatic animation (e.g. moving or replacing rendered objects). | uaag-2 | |||||||||||||||||||||||
26 | Anxiety Disorders | People who have anxiety disorders struggle with intense and uncontrollable feelings of anxiety, fear, worry, and/or panic. This is more than just feeling worried once in a while. This may last for a long time and can interfere with daily activities, such as concentration and executive function. | content-usable | |||||||||||||||||||||||
27 | application programming interface (API) | A mechanism that defines how communication can take place between applications. | uaag-2 | |||||||||||||||||||||||
28 | Appropriate field for the form control | The field name of the form control is appropriate if it is listed in the autocomplete fields table from the HTML 5.2 specification as applying to the specified control group. https://html.spec.whatwg.org/#inappropriate-for-the-control. | act-rules | |||||||||||||||||||||||
29 | ASCII art | picture created by a spatial arrangement of characters or glyphs (typically from the 95 printable characters defined by ASCII) | wcag-2 | |||||||||||||||||||||||
30 | Assistive Technologies assistive technology | Hardware and/or software that: relies on services provided by a user agent to retrieve and render Web content works with a user agent or web content itself through the use of APIs, and provides services beyond those offered by the user agent to facilitate user interaction with web content by people with disabilities This definition may differ from that used in other documents. Examples of assistive technologies that are important in the context of this document include the following: screen magnifiers, which are used to enlarge and improve the visual readability of rendered text and images; screen readers, which are most-often used to convey information through synthesized speech or a refreshable Braille display; text-to-speech software, which is used to convert text into synthetic speech; speech recognition software, which is used to allow spoken control and dictation; alternate input technologies (including head pointers, on-screen keyboards, single switches, and sip/puff devices), which are used to simulate the keyboard; alternate pointing devices, which are used to simulate mouse pointing and clicking. | aria-common | |||||||||||||||||||||||
31 | assistive technology | For the purpose of UAAG 2.0 conformance, assistive technology meets the following criteria: Relies on services (such as retrieving web resources and parsing markup) provided by one or more host user agents. Communicates data and messages with host user agents by monitoring and using APIs. Provides services beyond those offered by the host user agents to meet the requirements of users with disabilities. Additional services include alternative renderings (e.g. as synthesized speech or magnified content), alternative input methods (e.g. voice), additional navigation or orientation mechanisms, and content transformations (e.g. to make tables more accessible). Examples of assistive technologies that are important in the context of UAAG 2.0 include the following: Screen magnifiers, which are used by people with visual disabilities to enlarge and change colors on the screen to improve the visual readability of rendered text and images. Screen readers, which are used by people who are blind or have reading disabilities to read textual information through synthesized speech or braille displays. Voice recognition software, which is used by some people who have physical disabilities to simulate the keyboard and mouse. Alternative keyboards, which are used by some people with physical disabilities to simulate the keyboard and mouse. Alternative pointing devices, which are used by some people with physical disabilities to simulate mouse pointing and button activations. | uaag-2 | |||||||||||||||||||||||
32 | assistive technology | Software (or hardware), separate from the authoring tool, that provides functionality to meet the requirements of people with disabilities (authors and end users). Some authoring tools may also provide direct accessibility features. Examples include: screen magnifiers, and other visual reading assistants, which are used by people with visual, perceptual, and physical print disabilities to change text font, size, spacing, color, synchronization with speech, etc. in order improve the visual readability of rendered text and images; screen readers, which are used by people who are blind to read textual information through synthesized speech or Braille; text-to-speech software, which is used by some people with cognitive, language, and learning disabilities to convert text into synthetic speech; speech recognition software, which are used by some people who have some physical disabilities; alternative keyboards, which are used by some people with physical disabilities to simulate the keyboard (including alternate keyboards that use head pointers, single switches, sip/puff, and other special input devices); alternative pointing devices, which are used by some people with physical disabilities to simulate mouse pointing and button activations. | atag-2 | |||||||||||||||||||||||
33 | assistive technology assistive technology assistive technologies | Hardware and / or software that acts as a stand-alone user agent, or alongside a mainstream user agent to meet the functional requirements of users with disabilities that go beyond those provided by mainstream user agents alone. | captcha | |||||||||||||||||||||||
34 | assistive technology (as used in this document) assistive technologies | hardware and/or software that acts as a user agent, or along with a mainstream user agent, to provide functionality to meet the requirements of users with disabilities that go beyond those offered by mainstream user agents functionality provided by assistive technology includes alternative presentations (e.g., as synthesized speech or magnified content), alternative input methods (e.g., voice), additional navigation or orientation mechanisms, and content transformations (e.g., to make tables more accessible). Assistive technologies often communicate data and messages with mainstream user agents by using and monitoring APIs. The distinction between mainstream user agents and assistive technologies is not absolute. Many mainstream user agents provide some features to assist individuals with disabilities. The basic difference is that mainstream user agents target broad and diverse audiences that usually include people with and without disabilities. Assistive technologies target narrowly defined populations of users with specific disabilities. The assistance provided by an assistive technology is more specific and appropriate to the needs of its target users. The mainstream user agent may provide important functionality to assistive technologies like retrieving Web content from program objects or parsing markup into identifiable bundles. Assistive technologies that are important in the context of this document include the following: screen magnifiers, and other visual reading assistants, which are used by people with visual, perceptual and physical print disabilities to change text font, size, spacing, color, synchronization with speech, etc. in order to improve the visual readability of rendered text and images; screen readers, which are used by people who are blind to read textual information through synthesized speech or braille; text-to-speech software, which is used by some people with cognitive, language, and learning disabilities to convert text into synthetic speech; speech recognition software, which may be used by people who have some physical disabilities; alternative keyboards, which are used by people with certain physical disabilities to simulate the keyboard (including alternate keyboards that use head pointers, single switches, sip/puff and other special input devices.); alternative pointing devices, which are used by people with certain physical disabilities to simulate mouse pointing and button activations. | wcag-2 | |||||||||||||||||||||||
35 | Attention Deficit (Hyperactivity) disorder, AD(H)D Attention deficit disorder ADD Attention deficit hyperactivity disorder AD(H)D Attention Deficit Hyperactive Disorder Attention Deficit (Hyperactivity) disorder | Sometimes called “attention deficit disorder”, “ADD”, and “attention deficit hyperactivity disorder”, “ADHD”. Attention deficit (hyperactivity) disorder or AD(H)D involves difficulty focusing on a single task, focusing for longer periods, or being easily distracted. It is marked by an ongoing pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development. | content-usable | |||||||||||||||||||||||
36 | Attribute attribute attributes | In this specification, attribute is used as it is in markup languages. Attributes are structural features added to elements to provide information about the states and properties of the object represented by the element. | aria-common | |||||||||||||||||||||||
37 | Attribute value | The attribute value of a content attribute set on an HTML element is the value that the attribute gets after being parsed and computed according to specifications. It may differ from the value that is actually written in the HTML code due to trimming whitespace or non-digits characters, default values, or case-insensitivity. Some notable case of attribute value, among others: For enumerated attributes, the attribute value is either the state of the attribute, or the keyword that maps to it; even for the default states. Thus <input type="image" /> has an attribute value of either Image Button (the state) or image (the keyword mapping to it), both formulations having the same meaning; similarly, "an input element with a type attribute value of Text" can be either <input type="text" />, <input /> (missing value default), or <input type="invalid" /> (invalid value default). For boolean attributes, the attribute value is true when the attribute is present and false otherwise. Thus <button disabled>, <button disabled="disabled"> and <button disabled=""> all have a disabled attribute value of true. For attributes whose value is used in a case-insensitive context, the attribute value is the lowercase version of the value written in the HTML code. For attributes that accept numbers, the attribute value is the result of parsing the value written in the HTML code according to the rules for parsing this kind of number. For attributes that accept sets of tokens, whether space separated or comma separated, the attribute value is the set of tokens obtained after parsing the set and, depending on the case, converting its items to lowercase (if the set is used in a case-insensitive context). For aria-* attributes, the attribute value is computed as indicated in the WAI-ARIA specification and the HTML Accessibility API Mappings. This list is not exhaustive, and only serves as an illustration for some of the most common cases. The attribute value of an IDL attribute is the value returned on getting it. Note that when an IDL attribute reflects a content attribute, they have the same attribute value. | act-rules | |||||||||||||||||||||||
38 | audio | the technology of sound reproduction Audio can be created synthetically (including speech synthesis), recorded from real world sounds, or both. | wcag-2 | |||||||||||||||||||||||
39 | audio | The technology of sound transmission. Audio can be created synthetically (including speech synthesis), streamed from a live source (e.g. a radio broadcast), or recorded from real world sounds. There can be multiple audio tracks in a presentation. | uaag-2 | |||||||||||||||||||||||
40 | audio | The technology of sound reproduction. Audio can be created synthetically (including speech synthesis), recorded from real-world sounds, or both. | atag-2 | |||||||||||||||||||||||
41 | audio description | A type of alternative content that takes the form of narration added to the audio to describe important visual details that cannot be understood from the main soundtrack alone. Audio description of video provides information about actions, characters, scene changes, on-screen text, and other visual content. In standard audio description, narration is added during existing pauses in dialogue. extended audio description: An audio description in which the video is sometimes paused so that there is time to add additional description. | uaag-2 | |||||||||||||||||||||||
42 | audio description audio descriptions | narration added to the soundtrack to describe important visual details that cannot be understood from the main soundtrack alone Audio description of video provides information about actions, characters, scene changes, on-screen text, and other visual content. In standard audio description, narration is added during existing pauses in dialogue. (See also extended audio description.) Where all of the video information is already provided in existing audio, no additional audio description is necessary. Also called "video description" and "descriptive narration." | wcag-2 | |||||||||||||||||||||||
43 | Audio output | This test aspect includes all auditory data output from the web page into an audio channel. | act-rules | |||||||||||||||||||||||
44 | audio track | All or part of the audio portion of a presentation (e.g. each instrument can have a track, or each stereo channel can have a track). | uaag-2 | |||||||||||||||||||||||
45 | audio-only | a time-based presentation that contains only audio (no video and no interaction) | wcag-2 | |||||||||||||||||||||||
46 | author | A person who works alone or collaboratively to create content (e.g. content author, designer, programmer, publisher, tester). | uaag-2 | |||||||||||||||||||||||
47 | author actions preventing generation of accessible web content | When the actions of authors prevent authoring tools from generating accessible web content (WCAG). Examples include: turning off accessible content support features, ignoring prompts for accessibility information (WCAG), providing faulty accessibility information (WCAG) at prompts, modifying the authoring tool (e.g. via scripting, macros), and installing plug-ins. | atag-2 | |||||||||||||||||||||||
48 | author permission | Authorization that allows modification of given web content. | atag-2 | |||||||||||||||||||||||
49 | authoring action | Any action that authors can take using the authoring tool user interface that results in editing web content (e.g. typing text, deleting, inserting an element, applying a template). In contrast, most authoring tool user interfaces also enable actions that do not edit content (e.g. saving, publishing, setting preferences, viewing documentation). reversible authoring action: An authoring action that can be immediately and completely undone by the authoring tool upon a cancel request by an author. Examples of cancel requests include: "cancel", "undo", "redo" (when it used to reverse "undo"), "revert", and "roll-back" Note: It is acceptable for an authoring tool to collect a series of text entry actions (e.g. typed words, a series of backspaces) into a single reversible authoring action. | atag-2 | |||||||||||||||||||||||
50 | authoring outcome | The content or content modifications that result from authoring actions. Authoring outcomes are cumulative (e.g. text is entered, then styled, then made into a link, then given a title). | atag-2 | |||||||||||||||||||||||
51 | authoring practice | An approach that authors follow to achieve a given authoring outcome (e.g. controlling presentation with style sheets). Depending on the design of an authoring tool, authoring practices may be chosen by authors or by the authoring tool. Authoring practices may or may not be: accessible authoring practices (WCAG): An authoring practice in which the authoring outcome conforms to WCAG 2.0 at Level A, AA, or AAA. Some accessible authoring practices require accessibility information (WCAG). | atag-2 | |||||||||||||||||||||||
52 | authoring session | A state of the authoring tool in which web content can be edited by an author. end of an authoring session: The point at which the author has no further opportunity to make authoring actions without starting another session. The end of an authoring session may be determined by authors (e.g. closing a document, publishing) or by the authoring tool (e.g. when the authoring tool transfers editing permission to another author on a collaborative system). Note: The end of the authoring session is distinct from publishing. Automatic content generation may continue after the end of both the authoring session and initial publishing (e.g. content management system updates). | atag-2 | |||||||||||||||||||||||
53 | authoring tool | Any web-based or non-web-based application(s) that can be used by authors (alone or collaboratively) to create or modify web content for use by other people (other authors or end users). Note 1: "application(s)": ATAG 2.0 may be conformed to by stand-alone applications or by collections of applications. If a conformance claim is made, then the claim must provide identifying information for each application and also for any required extensions, plug-ins, etc. Note 2: "alone or collaboratively": Multiple authors may contribute to the creation of web content and, depending on the authoring tool, each author may work with different views of the content and different author permissions. Note 3: "to create or modify web content": This clause rules out software that collects data from a person for other purposes (e.g. online grocery order form) and then creates web content from that data (e.g. a web-based warehouse order) without informing the person (however, WCAG 2.0 would still apply). This clause also rules out software used to create content exclusively in non-web content technologies. Note 4: "for use by other people": This clause rules out the many web applications that allow people to modify web content that only they themselves experience (e.g. web-based email display settings) or that only provide input to automated processes (e.g. library catalog search page). Examples of software that are generally considered authoring tools under ATAG 2.0: web page authoring tools (e.g. WYSIWYG HTML editors) software for directly editing source code software for converting to web content technologies (e.g. "Save as HTML" features in office document applications) integrated development environments (e.g. for web application development) software that generates web content on the basis of templates, scripts, command-line input or "wizard"-type processes software for rapidly updating portions of web pages (e.g. blogging, wikis, online forums) software for generating/managing entire websites (e.g. content management systems, courseware tools, content aggregators) email clients that send messages using web content technologies multimedia authoring tools software for creating mobile web applications Examples of software that are not considered authoring tools under ATAG 2.0 (in all cases, WCAG 2.0 still applies if the software is web-based): customizable personal portals: ATAG 2.0 does not apply because the web content being edited is only available to the owner of the portal e-commerce order forms: ATAG 2.0 does not apply because the purpose of an e-commerce order form is to order a product, not communicate with other people via web content, even if the data collected by the form actually does result in web content (e.g. online tracking pages) stand-alone accessibility checkers: ATAG 2.0 does not apply because a stand-alone accessibility checker with no automated or semi-automated repair functionality does not actually modify web content. An accessibility checker with repair functionality or that is considered as part of a larger authoring process would be considered an authoring tool. | atag-2 | |||||||||||||||||||||||
54 | authoring tool user interface | The display and control mechanism that authors use to operate the authoring tool software. User interfaces may be non-web-based or web-based or a combination (e.g. a non-web-based authoring tool might have web-based help pages): authoring tool user interface (non-web-based): Any parts of an authoring tool user interface that are not implemented as web content and instead run directly on a platform that is not a user agent (e.g. Windows, Mac OS, Java Virtual Machine, iOS, Android). authoring tool user interface (web-based): Any parts of an authoring tool user interface that are implemented using web content technologies and are accessed by authors via a user agent. Authoring tool user interfaces may or may not be: accessible authoring tool user interfaces: Authoring tool user interfaces that meet the success criteria of a level in Part A of ATAG 2.0. | atag-2 | |||||||||||||||||||||||
55 | authors | People who use authoring tools to create or modify web content. The term may cover roles such as content authors, designers, programmers, publishers, testers, etc. (see Part B Conformance Applicability Note 6: Multiple authoring roles). Some authoring tools control who may be an author by managing author permissions. | atag-2 | |||||||||||||||||||||||
56 | Autistic Autism spectrum disorder ASD autism asperger syndrome pervasive developmental disorder | Sometimes called “autism spectrum disorder”, “ASD”, “autism”, “asperger syndrome”, and “pervasive developmental disorder”. Autistic people have some degree of impaired social behavior, communication and language abilities. This may also impact the person’s ability to regulate behavior and attention. Individuals can have a narrow range of interests and activities and they may rely on alternative communication methods. Some individuals may also experience episodes of sensory overload. See neurodiversity for an alternative approach to autism and learning and cognitive disabilities. | content-usable | |||||||||||||||||||||||
57 | Automated evaluation Automated Automatically evaluated Automated testing Automatically tested | Evaluation conducted using software tools, typically evaluating code-level features and applying heuristics for other tests. Automated testing is contrasted with other types of testing that involve human judgement or experience. Semi-automated evaluation allows machines to guide humans to areas that need inspection. The emerging field of testing conducted via machine learning is not included in this definition. | wcag-3 | |||||||||||||||||||||||
58 | available printing devices | Printing devices that are identified as available to applications via the platform. | uaag-2 | |||||||||||||||||||||||
59 | Background Colors Of Text | The colors of all pixels, excluding the foreground colors pixels, in the bounding box around a visible character in a text node. | act-rules | |||||||||||||||||||||||
60 | Bayesian filter Bayesian filter Bayesian filtering | Recursive probabilistic heuristic to categorize content, typically used in spam filtering. | captcha | |||||||||||||||||||||||
61 | blinking | switch back and forth between two visual states in a way that is meant to draw attention See also flash. It is possible for something to be large enough and blink brightly enough at the right frequency to be also classified as a flash. | wcag-2 | |||||||||||||||||||||||
62 | Block of content | A block of content in an HTML web page is a set of nodes from that page for which all the following are true: content: there is at least one node which is perceivable content in the block; and continuity: if two nodes are in the block, then any node between them (in tree order) is also in the block; and downward closure: if a node is in the block, then all its descendants are also in the block; and parent closure: if all children of a node are in the block, then this node is also in the block. Assumptions for Block of content This definition assumes that the rendering order of nodes on a page does not greatly differ from the DOM tree order. Otherwise, blocks of content as defined here may be different from what is visually perceived as "content in a close relationship". | act-rules | |||||||||||||||||||||||
63 | Block of repeated content | A block of content B, inside an HTML web page P, is a block of repeated content if both the following are true: distance 1: there exist an instrument in P which leads the user to another HTML web page P' whose URL has a different host, port (including default port for special URL), or path; and repeated: there exist a block of content in P' which is equivalent to B. Background for Block of repeated content This definition only considers pages at "distance 1" from the current page. The instrument leading there is usually a link, sometimes a button. In addition, P' can be any page and is not restricted, for example, to pages of the same website. The blocks of repeated content are not uniquely defined. For example <div><span id="repeated-1"></span><span id="repeated-2"></span><span id="not-repeated"></span></div> can be considered to have two blocks of repeated content (each of the first two span) or one (both the first two span together). | act-rules | |||||||||||||||||||||||
64 | Blocked event | A blocked event makes no changes to the content of the web page. | act-rules | |||||||||||||||||||||||
65 | blocks of text | more than one sentence of text | wcag-2 | |||||||||||||||||||||||
66 | Bounding Box around Text | The smallest rectangle that encloses all the visible pixels of a character (including anti-aliased pixels), plus one pixel on every edge (top, right, bottom, left), aligned on the horizontal and vertical axis. | act-rules | |||||||||||||||||||||||
67 | Brain Injury | Brain injury including, traumatic brain injury (TBI) and acquired brain injury (ABI), are caused by damage to the brain which can lead to long-term impairment of executive function, memory, learning, coordination, speech, and emotions as well as other physical and sensory impairments. Brain injury can have many different causes such as a concussion or stroke, and can happen at any stage of life. | content-usable | |||||||||||||||||||||||
68 | CAPTCHA | initialism for "Completely Automated Public Turing test to tell Computers and Humans Apart" CAPTCHA tests often involve asking the user to type in text that is displayed in an obscured image or audio file. A Turing test is any system of tests designed to differentiate a human from a computer. It is named after famed computer scientist Alan Turing. The term was coined by researchers at Carnegie Mellon University. | wcag-2 | |||||||||||||||||||||||
69 | CAPTCHA CAPTCHA Completely Automated Public Turing Test to Tell Computers and Humans Apart | “Completely Automated Public Turing Test to distinguish between Computers and Humans” relying on a challenge believed to be difficult for machines to satisfy correctly but relatively easy for humans. | captcha | |||||||||||||||||||||||
70 | captions | synchronized visual and/or text alternative for both speech and non-speech audio information needed to understand the media content Captions are similar to dialogue-only subtitles except captions convey not only the content of spoken dialogue, but also equivalents for non-dialogue audio information needed to understand the program content, including sound effects, music, laughter, speaker identification and location. Closed Captions are equivalents that can be turned on and off with some players. Open Captions are any captions that cannot be turned off. For example, if the captions are visual equivalent images of text embedded in video. Captions should not obscure or obstruct relevant information in the video. In some countries, captions are called subtitles. Audio descriptions can be, but do not need to be, captioned since they are descriptions of information that is already presented visually. | wcag-2 | |||||||||||||||||||||||
71 | captions | A type of alternative content that takes the form of text presented and synchronized with time-based media to provide not only the speech, but also non-speech information conveyed through sound, including meaningful sound effects and identification of speakers. In some countries, the term "subtitle" is used to refer to dialogue only and "captions" is used as the term for dialogue plus sounds and speaker identification. In other countries, "subtitle" (or its translation) is used to refer to both. open captions: Captions that are always rendered with a visual track; they cannot be turned off. closed captions: Captions that can be turned on and off. The captions requirements of UAAG 2.0 assume that the user agent can recognize the captions as such. Note: Other terms that include the word "caption" can have different meanings. For instance, a "table caption" is a title for a table, often positioned graphically above or below the table. | uaag-2 | |||||||||||||||||||||||
72 | Changes in content | A event originated change in the content of a web page occurs when, by comparing the web page before and 1 minute after the event firing, at least one of the following occurs: visible changes: the rendered pixels change in any part of the document that is currently within the viewport or that can be brought into the viewport via scrolling; or accessibility tree changes: any state, property or event of a node representing an accessible object of the accessibility tree changes, or any node is inserted in, or removed from the accessibility tree; or audible changes: the audio rendered by the web page changes. If the web page is rendering time-based media, rendered pixels and audio will be changing as part of the playback. The comparison in this instance should compare the pixels and audio that are rendered if the event is not fired, with the ones that are rendered if the event is fired. Assumptions: This definition assumes that there are no changes in the content of the web page caused by another event. If this is not the case, changes may be attributed to the wrong event. This definition assumes that the changes happen within a 1 minute time span after the event firing and therefore the comparison between the page before and after the event firing can be made at any time after that time span elapses. If there are changes after this time span, this definition may not detect them. The arbitrary 1 minute time span, selected so that testing this rule would not be impractical, is not included in WCAG. | act-rules | |||||||||||||||||||||||
73 | changes of context change of context | major changes in the content of the Web page that, if made without user awareness, can disorient users who are not able to view the entire page simultaneously Changes in context include changes of: user agent; viewport; focus; content that changes the meaning of the Web page A change of content is not always a change of context. Changes in content, such as an expanding outline, dynamic menu, or a tab control do not necessarily change the context, unless they also change one of the above (e.g., focus). Opening a new window, moving focus to a different component, going to a new page (including anything that would look to a user as if they had moved to a new page) or significantly re-arranging the content of a page are examples of changes of context. | wcag-2 | |||||||||||||||||||||||
74 | checking, accessibility | The process by which web content is evaluated for web content accessibility problems (WCAG). ATAG 2.0 recognizes three types of checking, based on increasing levels of automation of the tests: manual checking: Checking in which the tests are carried out by authors. This includes the case where authors are aided by instructions or guidance provided by the authoring tool, but where authors must carry out the actual test procedure. semi-automated checking: Checking in which the tests are partially carried out by the authoring tool, but where authors' input or judgment is still required to decide or help decide the outcome of the tests. automated checking: Checking in which the tests are carried out automatically by the authoring tool without any intervention by authors. An authoring tool may support any combination of checking types. | atag-2 | |||||||||||||||||||||||
75 | Class class classes | A set of instance objects that share similar characteristics. | aria-common | |||||||||||||||||||||||
76 | Clearly labeled location | Secondary information and alternative controls of functionality are often not displayed together with primary information or functionality. For example, an option to change a web page to dark mode may be placed on an options page instead of being available on every page and page state of a website. Another example is a maps application, where, instead of using GPS, an option is available in a dropdown menu to set the current location of the device. Such content should be placed in a clearly labeled location. The location of a target is said to be clearly labeled when the target can be found by activating "identifiable" instruments which either lead the user to find the target, or to another page or page state from which this action can be repeated until the target is found. Whether or not the content is "clearly labeled" depends on the starting point of the search. If page A has a link which clearly "identifies" some piece of content, then the location of the content is clearly labeled. Page B, which can be in the same website, may not have such a link or may have a link with a link text that does not "identify" target content or which can be interpreted to "identify" more than one target, and so the location of the content starting from page B is not clearly labeled. For the purpose of this definition, an instrument is identifiable if any text or other content with a text alternative, allows any user to identify an element with a semantic role that inherits from widget. A web page changes state when the document's body changes without a change in the document's URL. | act-rules | |||||||||||||||||||||||
77 | Clipped by Overflow | A node with an ancestor in the flat tree with a computed overflow of none or clipped, where changing the overflow of all such ancestors to visible would cause more of the node to become visible. Example of clipped by overflow for Clipped by Overflow This img element has an ancestor div element with an overflow of none (both overflow-x and overflow-y). The height of the img is greater than that of the ancestor div, and so is clipped by the overflow property of the div. <div style = " height : 100px; overflow : none; " > <img src = "/test-assets/w3c-logo.png" height = "150" alt = "Partial W3C Logo" /> </div > | act-rules | |||||||||||||||||||||||
78 | Cognitive and Learning Disabilities cognitive disabilities learning disabilities LD intellectual disabilities specific learning disabilities | May include: cognitive disabilities, learning disabilities (LD), intellectual disabilities and specific learning disability. Cognitive disabilities and learning disabilities can mean different things in different locations. Taken together they refer to: significantly reduced ability in one or more areas of cognitive function that affect learning, such as communication, reading, writing, or math. Note overall intelligence is often not affected and people may function any level in other areas of learning. (Sometimes called learning disability or specific learning disability), and / or significantly reduced ability to understand new or complex information and learn new skills, with a reduced ability to cope independently. (Sometimes called cognitive disability, learning disability or intellectual disability), and / or significantly reduced memory and attention or visual, language, or numerical thinking. | content-usable | |||||||||||||||||||||||
79 | Cognitive function test cognitive function test | New A task that requires the user to remember, manipulate, or transcribe information. Examples include, but are not limited to: memorization, such as remembering a username, password, set of characters, images, or patterns. The common identifiers name, e-mail, and phone number are not considered cognitive function tests as they are personal to the user and consistent across websites; transcription, such as typing in characters; use of correct spelling; performance of calculations; solving of puzzles. | wcag-2 | |||||||||||||||||||||||
80 | commands | Actions made by users to control the user agent. These include: direct commands: Commands that apply to a specified item (e.g. button) or action (e.g. save function), regardless of the current focus location. Also see keyboard command direct navigation commands: Commands that move focus to a specified item. direct activation commands: Commands that activate the specified item (and can also move focus to it) or action. sequential navigation commands (sometimes called "logical navigation commands" or "linear navigation commands"): Commands that move focus forwards and backwards through a list of items. The element list being navigated can be the list of all elements or just a subset (e.g. the list of headers, the list of links). spatial commands (sometimes called "directional commands"): Commands that require the user to be aware of the spatial arrangement of items on the screen: spatial navigation commands: Commands that move from one item to another based on direction on the screen. spatial manipulation commands: Commands that resize or reposition an item on the screen. structural navigation commands: Commands that move forwards, backwards, up and down a hierarchy. | uaag-2 | |||||||||||||||||||||||
81 | Conformance Conform | Satisfying all the requirements of the guidelines. Conformance is an important part of following the guidelines even when not making a formal Conformance Claim. See Conformance. | wcag-3 | |||||||||||||||||||||||
82 | conformance conform | satisfying all the requirements of a given standard, guideline or specification | wcag-2 | |||||||||||||||||||||||
83 | conforming alternate version conforming alternate versions | version that conforms at the designated level, and provides all of the same information and functionality in the same human language, and is as up to date as the non-conforming content, and for which at least one of the following is true: the conforming version can be reached from the non-conforming page via an accessibility-supported mechanism, or the non-conforming version can only be reached from the conforming version, or the non-conforming version can only be reached from a conforming page that also provides a mechanism to reach the conforming version In this definition, "can only be reached" means that there is some mechanism, such as a conditional redirect, that prevents a user from "reaching" (loading) the non-conforming page unless the user had just come from the conforming version. The alternate version does not need to be matched page for page with the original (e.g., the conforming alternate version may consist of multiple pages). If multiple language versions are available, then conforming alternate versions are required for each language offered. Alternate versions may be provided to accommodate different technology environments or user groups. Each version should be as conformant as possible. One version would need to be fully conformant in order to meet conformance requirement 1. The conforming alternative version does not need to reside within the scope of conformance, or even on the same Web site, as long as it is as freely available as the non-conforming version. Alternate versions should not be confused with supplementary content, which support the original page and enhance comprehension. Setting user preferences within the content to produce a conforming version is an acceptable mechanism for reaching another version as long as the method used to set the preferences is accessibility supported. See Understanding Conforming Alternate Versions | wcag-2 | |||||||||||||||||||||||
84 | content (structured) | Web content that includes machine-readable internal structure (e.g. markup elements), as opposed to unstructured content, such as raster image formats or plain human language text. | atag-2 | |||||||||||||||||||||||
85 | content (Web content) | information and sensory experience to be communicated to the user by means of a user agent, including code or markup that defines the content's structure, presentation, and interactions | wcag-2 | |||||||||||||||||||||||
86 | content (web content) | Information and sensory experience to be communicated to the user by means of a user agent, including code or markup that defines the content's structure, presentation, and interactions. | uaag-2 | |||||||||||||||||||||||
87 | content (web content) | Information and sensory experience to be communicated to the end user by means of a user agent, including code or markup that defines the content's structure, presentation, and interactions. In ATAG 2.0, the term is primarily used to refer to the output that is produced by the authoring tool. Content produced by authoring tools may include web applications, including those that act as web-based authoring tools. Content may or may not be: accessible content (WCAG): Content that would conform to WCAG 2.0, at either Level A, AA, or AAA, assuming that any web content technologies relied upon to satisfy the WCAG 2.0 success criteria are accessibility supported. Note 1: If accessibility support for the relied upon technologies is lacking, then the content will not conform to WCAG 2.0 and one or more groups of end users with disabilities will likely experience difficulty accessing the content. Note 2: Conformance to WCAG 2.0, even at the highest level (i.e. Level AAA), still may not make content "accessible to individuals with all types, degrees, or combinations of disability". content being edited: The web content that an author can modify during an authoring session. The content being edited may be a complete piece of content (e.g. image, style sheet) or only part of a larger piece of content (e.g. a status update). The content being edited only includes content in web content technologies that the authoring tool supports (e.g. a WYSIWYG HTML editor allows editing of the HTML content of a web page editable, but not the images). | atag-2 | |||||||||||||||||||||||
88 | content generation (content authoring, content editing) | The act of specifying the actual web content that will be rendered, played or executed by the end user's user agent. While the precise details of how content is created in any given system may vary widely, responsibility for the generation of content can be any combination of the following: author generated content: Web content for which authors are fully responsible. The author may only be responsible down to a particular level (e.g. when asked to type a text label, the author is responsible for the text, but not for how the label is marked up; when typing markup in a source editing-view, the author is not responsible for the fact that UNICODE is used to encode the text ). automatically-generated content: Web content for which developer-programmed functionality is fully responsible (e.g. what markup to output when an author requests to start a new document, automatically correcting markup errors). third-party content generation: Web content for which a third-party author is responsible (e.g. community shared templates). | atag-2 | |||||||||||||||||||||||
89 | content properties | The individual pieces of information that make up the web content (e.g. the attributes and contents of elements, style sheet information). | atag-2 | |||||||||||||||||||||||
90 | content rendering | User interface functionality that authoring tools present if they render, play or execute the web content being edited. ATAG 2.0 recognizes several types of content renderings: conventional renderings (or "WYSIWYG"): When content is rendered in a way that is similar to the default rendering a user agent would create from the same content. While "WYSIWYG", standing for "What-you-see-is-what-you-get" is the common term, differences between user agents and end user settings mean that in reality there is no single typical end user experience; or unconventional renderings: When content is rendered differently than it would be in a typical user agent (e.g. rendering an audio file as a graphical waveform); or partial renderings: When some aspects of the content are rendered, played, or executed, but not others (e.g. a frame-by-frame video editor renders the graphical, but not the timing aspects, of a video). | atag-2 | |||||||||||||||||||||||
91 | content transformations | Processes that take content in one web content technology or non-web content technology (e.g. a word processing format) as input and produce content that has been optimized, restructured or recoded: Optimizing Content Transformations: Transformations in which the content technology is not changed and the structural features of the content technology that are employed also stay the same. Changes would not be expected to result in information loss (e.g. removing whitespace, replacing in-line styles with an external style sheet). Restructuring Content Transformations: Transformations in which the content technology stays the same, but the structural features of the technology used to markup the content are changed (e.g. linearizing tables, splitting a document into pages. Recoding Content Transformations: Transformations in which the content technology used to encode the content is changed (e.g. HTML to XHTML, a word processing format to HTML). Note: Clipboard operations, in which content is copied to or pasted from the platform clipboard, are not considered content transformations. | atag-2 | |||||||||||||||||||||||
92 | context-sensitive help | help text that provides information related to the function currently being performed Clear labels can act as context-sensitive help. | wcag-2 | |||||||||||||||||||||||
93 | continuous authentication | Mechanism to determine that a user is still the one previously verified without requiring interactive re-authentication. | captcha | |||||||||||||||||||||||
94 | continuous scale | When interacting with a time-based media presentation, a continuous scale allows user (or programmatic) action to set the active playback position to any time point on the presentation time line. The granularity of the positioning is determined by the smallest resolvable time unit in the media timebase. | uaag-2 | |||||||||||||||||||||||
95 | contrast ratio | (L1 + 0.05) / (L2 + 0.05), where L1 is the relative luminance of the lighter of the colors, and L2 is the relative luminance of the darker of the colors. Contrast ratios can range from 1 to 21 (commonly written 1:1 to 21:1). Because authors do not have control over user settings as to how text is rendered (for example font smoothing or anti-aliasing), the contrast ratio for text can be evaluated with anti-aliasing turned off. For the purpose of Success Criteria 1.4.3 and 1.4.6, contrast is measured with respect to the specified background over which the text is rendered in normal usage. If no background color is specified, then white is assumed. Background color is the specified color of content over which the text is to be rendered in normal usage. It is a failure if no background color is specified when the text color is specified, because the user's default background color is unknown and cannot be evaluated for sufficient contrast. For the same reason, it is a failure if no text color is specified when a background color is specified. When there is a border around the letter, the border can add contrast and would be used in calculating the contrast between the letter and its background. A narrow border around the letter would be used as the letter. A wide border around the letter that fills in the inner details of the letters acts as a halo and would be considered background. WCAG conformance should be evaluated for color pairs specified in the content that an author would expect to appear adjacent in typical presentation. Authors need not consider unusual presentations, such as color changes made by the user agent, except where caused by authors' code. | wcag-2 | |||||||||||||||||||||||
96 | control settings | Settings that relate to how authors operate the authoring tool, for example using the keyboard or mouse. | atag-2 | |||||||||||||||||||||||
97 | Correct autocomplete field | Any field name listed in the autocomplete fields table from the HTML 5.2 specification: https://html.spec.whatwg.org/#autofill-field | act-rules | |||||||||||||||||||||||
98 | correct reading sequence | any sequence where words and paragraphs are presented in an order that does not change the meaning of the content | wcag-2 | |||||||||||||||||||||||
99 | Critical error Critical errors Critical failure Critical failures | An accessibility problem that will stop a user from being able to complete a process. Critical errors include: Items that will stop a user from being able to complete the task if it exists anywhere on the view (examples: flashing, keyboard trap, audio with no pause); Errors that when located within a process means the process cannot be completed (example: submit button not in tab order); Errors that when aggregated within a view or across a process cause failure (example: a large amount of confusing, ambiguous language). | wcag-3 | |||||||||||||||||||||||
100 | CSS pixel CSS pixels | visual angle of about 0.0213 degrees A CSS pixel is the canonical unit of measure for all lengths and measurements in CSS. This unit is density-independent, and distinct from actual hardware pixels present in a display. User agents and operating systems should ensure that a CSS pixel is set as closely as possible to the CSS Values and Units Module Level 3 reference pixel [[!css3-values]], which takes into account the physical dimensions of the display and the assumed viewing distance (factors that cannot be determined by content authors). | wcag-2 |