Web Accessibility Standards

Principle 1: Perceivable Guidelines

WCAG Perceivable Success Criteria (new window)
Information and user interface components must be presentable to users in ways they can perceive. This means that users must be able to perceive the information being presented. User agents, like screen readers, require clearly defined HTML elements within a structured web page. The ARIA (Accessibility Rich Internet Application) Landmarks and a hierarchy of Headers should be used to define page regions and content context. The Banner, Navigation panel, Main section, and Footer are visually perceivable on a standard computer screen, but not necessarily on a screen reader device.

Guideline 1.1 Text Alternatives

The intent of this Success Criterion is to make information conveyed by non-text content, such as images, accessible through the use of a text alternative. Text alternatives are a primary way for making information accessible because they can be rendered through any sensory modality (for example, visual, auditory or tactile) to match the needs of the user. That is, a person who cannot see a picture can have the text alternative read aloud using synthesized speech. A person who cannot hear an audio file can have the text alternative displayed so that he or she can read it.

Guideline 1.2 Time-based Media

The intent of this Success Criterion is to make information conveyed by prerecorded audio-only and prerecorded video-only content available to all users. An example of pre-recorded video with no audio information or user interaction is a silent movie. The purpose of the transcript is to provide an equivalent to what is presented visually. For prerecorded video content, authors have the option to provide an audio track. The purpose of the audio alternative is to be an equivalent to the video. This makes it possible for users with and without vision impairment to review content simultaneously. The approach can also make it easier for those with cognitive, language and learning disabilities to understand the content because it would provide parallel presentation.

Guideline 1.3 Adaptable

Create content that can be presented in different ways (for example simpler layout) without losing information or structure. The intent of this Success Criterion is to ensure that information and relationships that are implied by visual or auditory formatting are preserved when the presentation format changes. Sighted users perceive structure and relationships through various visual cues — headings are often in a larger, bold font separated from paragraphs by blank lines; list items are preceded by a bullet and perhaps indented; paragraphs are separated by a blank line; items that share a common characteristic are organized into tabular rows and columns; form fields may be positioned as groups that share text labels; a different background colour may be used to indicate that several items are related to each other; words that have special status are indicated by changing the font family and /or bolding, italicizing, or underlining them; items that share a common characteristic are organized into a table where the relationship of cells sharing the same row or column and the relationship of each cell to its row and/or column header are necessary for understanding; and so on. Having these structures and these relationships programmatically determined or available in text ensures that information important for comprehension will be perceivable to all.

Guideline 1.4 Distinguishable

Make it easier for users to see and hear content. The intent of this Success Criterion is to ensure that all users can access information that is conveyed by colour differences. If the information is conveyed through colour differences in an image (or other non-text format), the colour may not be seen by users with colour deficiencies. In this case, providing the information conveyed with colour through another visual means ensures users who cannot see colour can still perceive the information. Playing audio automatically when landing on a page may affect a screen reader user’s ability to find the mechanism to stop it because they navigate by listening and automatically started sounds might interfere with that navigation. Individuals who use screen reading software can find it hard to hear the speech output if there is other audio playing at the same time. Therefore, it is important that the user be able to turn off the background sound or control the volume level. Also, the intent of this Success Criterion is to provide enough contrast between text and its background so that it can be read by people with moderately low vision (who do not use contrast-enhancing assistive technology). It is important that colour is not a key factor so that people who have a colour vision deficit will also have adequate contrast between the text and the background.

Principle 2: Operable Guidelines

WCAG Operable Success Criteria (new window)
User interface components and navigation must be operable. This means that users must be able to operate the interface. All web page elements must be operable by a keyboard, speech input, and other non-mouse devices. Some of the Java scripts may not be keyboard accessible, and preventing non-mouse users from performing some functions. Many people do not use the mouse and rely on the keyboard to interact with the web. This requires keyboard access to all functionality, including form controls, input, and other user interface components.

Guideline 2.1 Keyboard Accessible

The intent of this Success Criterion is to ensure that, wherever possible, content can be operated through a keyboard or keyboard interface (so an alternate keyboard can be used). When content can be operated through a keyboard or alternate keyboard, it is operable by people with no vision (who cannot use devices such as mice that require eye-hand coordination) as well as by people who must use alternate keyboards or input devices that act as keyboard emulators. Keyboard emulators include speech input software, sip-and-puff software, on-screen keyboards, scanning software and a variety of assistive technologies and alternate keyboards. Individuals with low vision also may have trouble tracking a pointer and find the use of software much easier (or only possible) if they can control it from the keyboard.

Guideline 2.2 Enough Time

The intent of this Success Criterion is to ensure that users with disabilities are given adequate time to interact with web content whenever possible. People with disabilities such as blindness, low vision, dexterity impairments, and cognitive limitations may require more time to read content or to perform functions such as filling out on-line forms. If web functions are time-dependent, it will be difficult for some users to perform the required action before a time limit occurs. This may render the service inaccessible to them. Providing options to disable time limits, customize the length of time limits, or request more time before a time limit occurs helps those users who require more time than expected to successfully complete tasks. Also, avoid distracting users during their interaction with a web page; such as moving, blinking, scrolling and auto-updating content. Allow users to turn off content updates, except in emergencies. This allows access by people with cognitive limitations or attention disorders by enabling them to focus on the content. It also allows users who are blind or have low vision to keep their “viewing” focus on the content they are currently reading.

Guideline 2.3 Seizures and Physical Reactions

The intent of this Success Criterion is to allow users to access the full content of a site without inducing seizures due to photosensitivity. Individuals who have photosensitive seizure disorders can have a seizure triggered by content that flashes at certain frequencies for more than a few flashes. Some users experience distraction or nausea from animated content. For example, if scrolling a page causes elements to move (other than the essential movement associated with scrolling) it can trigger vestibular disorders. Vestibular (inner ear) disorder reactions include dizziness, nausea and headaches. Another animation that is often non-essential is parallax scrolling. Parallax scrolling occurs when backgrounds move at a different rate to foregrounds. allow users to prevent animation from being displayed on web pages.

Guideline 2.4 Navigable

Provide ways to help users navigate, find content, and determine where they are. A sighted user can ignore repeated content either by focusing on the center of the screen (where main content usually appears) or a mouse user can select a link with a single mouse click rather than encountering every link or form control that comes before the item they want. Likewise, it is important to allow people who navigate sequentially through content with a keyboard more direct access to the primary content of the web page.

Skipping repeated blocks of content, like navigation links, heading graphics, and advertising frames. Help users find content and orient themselves within the website by ensuring that each web page has a descriptive title. Titles identify the current location without requiring users to read or interpret page content. Ensure that when users navigate sequentially through content, they encounter information in an order that is consistent with the meaning of the content and can be operated from the keyboard. This reduces confusion by letting users form a consistent mental model of the content.

Help users understand the purpose of each link so they can decide whether they want to follow the link. Whenever possible, provide link text that identifies the purpose of the link without needing additional context. Assistive technology has the ability to provide users with a list of links that are on the web page. Link text that is as meaningful as possible will aid users who want to choose from this list of links. Also, the intent of this Success Criterion is to help users understand what information is contained in web pages and how that information is organized. When headings are clear and descriptive, users can find the information they seek more easily, and they can understand the relationships between different parts of the content more easily.

Descriptive labels help users identify specific components within the content. Labels and headings do not need to be lengthy. A word, or even a single character, may suffice if it provides an appropriate cue to finding and navigating content. It is important to help a person know which element among multiple elements on the page has the keyboard focus. If there is only one keyboard actionable control on the screen, the success criterion would be met because the visual design presents only one keyboard actionable item. Note that a keyboard focus indicator can take different forms. One common way is a caret within the text field to indicate that the text field has the keyboard focus. Another is a visual change to a button to indicate that the button has the keyboard focus.

Guideline 2.5 Input Modalities

Make it easier for users to operate functionality through various inputs beyond keyboard. The intent of this Success Criterion is to ensure that content can be controlled with a range of pointing devices, abilities, and assistive technologies. Some people cannot perform gestures in a precise manner, or they may use a specialized or adapted input device such as a head pointer, eye-gaze system, or speech-controlled mouse emulator. Some pointing methods lack the capability or accuracy to perform multipoint or path-based gestures. Make it easier for users to prevent accidental or erroneous pointer input. People with various disabilities can inadvertently initiate touch or mouse events with unwanted results.

Also, the intent of this Success Criterion is to ensure that the words which visually label a component are also the words associated with the component programmatically. This helps ensure that people with disabilities can rely on visible labels as a means to interact with the components. Most controls are accompanied by a visible text label. Those same controls have a programmatic name, also known as the Accessible Name. Users typically have a much better experience if the words and characters in the visible label of a control match the accessible name. When these match, speech-input users (using speech recognition applications) can navigate by speaking the visible text labels of components, such as menus, links, and buttons, that appear on the screen. Mismatches between visible labels and programmatic names for controls are even more of an issue for speech-input and text-to-speech users who also have cognitive challenges. Mismatches create an extra cognitive load for speech-input users, who must remember to say a speech command that is different from the visible label they see on a control. It also creates extra cognitive load for a text-to-speech user to absorb and understand speech output that does not match the visible label.

Principle 3: Understandable Guidelines

WCAG Understandable Success Criteria (new window)
Information and the operation of user interface must be understandable. This means that users must be able to understand the information as well as the operation of the user interface. Page Titles must be unique and meaningful. Links and Buttons must have concise and clearly marked text labels. Images must have descriptive alternative text. The page foreground and background – and icons – must have contrasting colours for low vision users. The web page must have clearly defined user instructions, and a separation of information content.

Guideline 3.1 Readable

Make text content readable and understandable. The first success criteria is to define the language of the page. This will ensure that content developers provide information in the web page that user agents need to present text and other linguistic content correctly. Both assistive technologies and conventional user agents can render text more accurately when the language of the web page is identified. Screen readers can load the correct pronunciation rules. Visual browsers can display characters and scripts correctly. Media players can show captions correctly. As a result, users with disabilities will be better able to understand the content.

Be shure to include a definition for words used in an unusual way or as an abbreviation (such as a link to a glossary or within the text context). Often words or characters have different meanings, each with its own pronunciation. The meaning of such words or characters can usually be determined from the context of the sentence. However, for more complex or ambiguous sentences, or for some languages, the meaning of the word cannot be easily determined or determined at all without knowing the pronunciation. When the sentence is read aloud and the screen reader reads the word using the wrong pronunciation, it can be even more difficult to understand than when read visually. When words are ambiguous or indeterminate unless the pronunciation is known, then providing some means of determining the pronunciation is needed.

Guideline 3.2 Predictable

Make web pages appear and operate in predictable ways. That is, ensure that functionality is predictable as visitors navigate their way through a document. Any component that is able to trigger an event when it receives focus must not change the context automatically (such as an automatically submitted form or automatically launching a new window, when a component receives focus). Changes in context can confuse users who do not easily perceive the change or are easily distracted by changes. Changes of context are appropriate only when it is clear that such a change will happen in response to the user’s action. So, clicking on links or tabs in a tab control is activating the control, not changing the setting of that control.

Also, it is important to design web pages with consistent presentation and layout for users who interact with repeated content within a set of web pages and need to locate specific information or functionality more than once. Individuals with low vision who use screen magnification to display a small portion of the screen at a time often use visual cues and page boundaries to quickly locate repeated content.

Guideline 3.3 Input Assistance

Ensure that users are aware that an error has occurred and can determine what is wrong. The error message should be as specific as possible. In the case of an unsuccessful form submission, re-displaying the form and indicating the fields in error is insufficient for some users to perceive that an error has occurred. Screen reader users, for example, will not know there was an error until they encounter one of the indicators. They may abandon the form altogether before encountering the error indicator, thinking that the page simply is not functional.

When possible ensure that users receive appropriate suggestions for correction of an input error. Content authors must present instructions or labels that identify the controls in a form so that users know what input data is expected. Instructions or labels may also specify data formats for fields especially if they are out of the customary formats or if there are specific rules for correct input. Users with disabilities may be more likely to make mistakes. People with reading disabilities may transpose numbers and letters, and those with motor disabilities may hit keys by mistake. Providing the ability to reverse actions allows users to correct a mistake that could result in serious consequences. Providing the ability to review and correct information gives the user an opportunity to detect a mistake before taking an action that has serious consequences. Help users avoid making mistakes by Using context-sensitive help, users can find out how to perform an operation without losing track of what they are doing.

Principle 4: Robustable Guidelines

WCAG Robust Success Criteria (new window)
Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, like browsers and assistive technologies. This means that users must be able to access the content as technologies advance. Meeting this requirement helps maximize compatibility with current and future user agents, like screen readers. In particular, it enables assistive technologies to process the content reliably, and to present or to operate it in different ways. This includes non-standard (scripted) buttons, input fields, and other controls. To deliver a desirable user experience, there must be a separation between web page design and user content. The web page may not render as expected in all browsers, and will not perform as expected in differing screen readers. A design utilizing style sheets and Java Script widgets may improve the robustness. Note, the Accessibility Rich Internet Application (ARIA) code should only be used on a web page if the native HTML code cannot implement the desired effect. ARIA code will not have any effect on older browsers.

Guideline 4.1 Parsing

Maximize compatibility with current and future user agents, including assistive technologies. The intent of this Success Criterion is to ensure that user agents, like browsers and screen readers, can accurately interpret and parse content. If the content cannot be parsed into a data structure, then different user agents may present it differently or be completely unable to parse it. Some user agents use repair techniques to render poorly coded content. In markup languages, errors in element and attribute syntax, and failure to provide properly nested start/end tags lead to errors that prevent user agents from parsing the content reliably. ensure that Assistive Technologies can gather information about, activate, and keep up to date on the status of user interface controls in the content.

When standard controls from accessible technologies are used, this process is straightforward. However, if custom controls are created, or interface elements are programmed (through scripts), to have a different role and/or function than usual, then additional measures need to be taken to ensure that the controls provide important information to assistive technologies and allow themselves to be controlled by assistive technologies. Also, it is important to make users aware of important changes in content that are not given focus, and to do so in a way that doesn’t unnecessarily interrupt their work. The scope of this Success Criterion is specific to changes in content that involve status messages.

Principle 5: Conformance Guidelines

WCAG Conformance Success Criteria (new window)
Conformance to a standard means that you meet or satisfy the requirements of the standard. In WCAG the requirements are the Success Criteria. To conform to WCAG, you need to satisfy the Success Criteria. In order to accommodate different situations that may require or allow greater levels of accessibility than others, WCAG has three levels of conformance. There are five requirements that must be met in order for content to be classified as conforming to WCAG.

Guideline 5.1 Conformance Level

The first requirement deals with the levels of conformance. It basically says that all information on a page conforms or has a conforming alternate version that is available from the page. One of the three levels of conformance (A, AA, AAA) must be met in full.

Guideline 5.2 Full Pages

This provision simply requires that the whole page conform. That is, statements about “part of a page conforming” cannot be made. For example, a long description of a graphic might be on a separate page that the user can jump to, or an alternative can also be provided on the same page.

Guideline 5.3 Complete Processes

When a web page is one of a series of web pages presenting a process (a sequence of steps that need to be completed in order to accomplish an activity), all web pages in the process must conform at the specified level or better. This would prevent a shopping site from being classified as conforming if the checkout or other features of the site that are part of the shopping and buying process do not conform.

Guideline 5.4 Only Accessibility-Supported Ways of Using Technologies

Only accessibility-supported ways of using technologies are relied upon to satisfy the success criteria. Many of the Success Criteria deal with providing accessibility through assistive technologies, or special accessibility features in mainstream user agents (for example, a show captions option in a media player). That is, the Success Criteria require that something be done in the web content that would make it possible for assistive technologies to successfully present the content’s information to the user. So, a picture that you were supposed to click on to go to a topic would not be accessible to a person who was blind, unless text alternatives describing the picture and the picture is defined as a Button, were provided in a way that user agents including assistive technologies can find and display them.

Guideline 5.5 Non-Interference

If technologies are used in a way that is not accessibility supported, then they must not block the ability of users to access the rest of the page. This means that technologies that are not accessibility supported can be used, as long as all the information is also available using technologies that are accessibility supported, and as long as the non-accessibility-supported material does not interfere.