Techniques for WCAG 2.0

The objective of this technique is to allow user to extend the default time-out by providing a mechanism to extend the time when scripts provide functionality that has default time-outs. In order to allow the user to request a longer than default time-out period, the script can provide a form (for example) allowing the user to enter a larger default time-out value. Making this available as a preference setting allows users to indicate their requirements in advance. If warning the user a time-out is about to expire (see Providing a script that warns the user a time-out is about to expire), this form can be made available from the warning dialog.

1. setting session and default time-outs using Java servlets

2. Overriding timeouts in peers applications

3. PHPBuilder Time-out Info

• Providing a script that warns the user a time-out is about to expire

Procedure

1. On a Web unit that uses scripts to enforce a time limit, wait until the time-out has expired.

2. Determine if an option was provided to extend the time-out.

Expected Results

• #2 is true and more time is provided to complete the interaction.

The objective of this technique is to display a dialog containing a message (alert) to the user. When the alert is displayed, it receives focus and the user must activate the OK button on the dialog to dismiss it. Since these alerts cause focus to change they may distract the user, especially when used for non-emergency information. Alerts for non-emergency purposes such as displaying a quote of the day, helpful usage tip, or count down to a particular event, are not presented unless the user enables them through an option provided in the Web unit.

This technique assigns a global JavaScript variable to store the user preference for displaying alerts. The default value is false. A wrapper function is created to check the value of this variable before displaying an alert. All calls to display an alert are made to this wrapper function rather than calling the alert() function directly. Early in the page, a button is provided for the user to enable the display of alerts on the page. This technique works on a visit by visit basis. Each time the page is loaded, alerts will be disabled and the user must manually enable them. Alternatively, the author could use cookies to store user preferences across sessions.

Procedure

For a Web unit that supports non-emergency interruptions using a JavaScript alert:

1. Load the Web unit and verify that no non-emergency alerts are displayed.

2. Verify there is a mechanism to activate the non-emergency alerts.

3. Activate the non-emergency alerts and verify that the alerts are displayed.

Expected Results

• For a Web unit that supports non-emergency interruptions using a JavaScript alert, checks 1, 2, and 3 above are true.

The objective of this technique is to notify users that they are almost out of time to complete an interaction. When scripts provide functionality that has time-outs, the script can include functionality to warn the user of imminent time-outs and provide a mechanism to request more time. 20 seconds or more before the time-out occurs, the script provides a confirm dialog that states that a time-out is imminent and asks if the user needs more time. If the user answers "yes" then the time-out is reset. If the user answers "no" or does not respond, the time-out is allowed to expire.

This technique involves time-outs set with the window.setTimeout() method. If, for example, the time-out is set to expire in 60 seconds, you can set the time-out for 40 seconds and provide the confirm dialog. When the confirm dialog appears, a new time-out is set for the remaining 20 seconds. Upon expiry of the "grace period time-out" the action that would have been taken at the expiry of the 60 second time-out in the original design is taken.

• Allowing the user to extend the default time-out

Procedure

On a Web unit that has a time-out controlled by a script:

1. load the page and start a timer that is 20 seconds less than the time-out.

2. when the timer expires, check that a confirmation dialog is displayed warning of the impending time-out.

Expected Results

• #2 is true.

The objective of this technique is to validate user input as values are entered for each field, by means of client-side scripting. If errors are found, an alert dialog describes the nature of the error in text. Once the user dismisses the alert dialog, it is helpful if the script positions the keyboard focus on the field where the error occurred.

• Providing expected data format and example

Procedure

For form fields that require specific input:

1. enter invalid data

2. determine if an alert describing the error is provided.

Expected Results

• #2 is true

The objective of this technique is to demonstrate how to correctly use an onchange event with a select element to update other elements on the Web unit. This technique will not cause a change of context. When there are one or more select elements on the Web unit, an onchange event on one, can update the options in another select element on the Web unit. All of the data required by the select elements is included within the Web unit.

It is important to note that the select item which is modified is after the trigger select element in the reading order of the Web unit. This ensures that assistive technologies will pick up the change and users will encounter the new data when the modified element receives focus. This technique relies on JavaScript support in the user agent.

(none currently listed)

Procedure

1. Navigate to the trigger select element (in this example, the one to select continents) and change the value of the select.

2. Navigate to the select element that is updated by the trigger (in this example, the one to select countries).

3. Check that the matching option values are displayed in the other select element.

4. Navigate to the trigger select element, navigate through the options but do not change the value.

5. Check that the matching option values are still displayed in the associated element.

It is recommended that the select elements are tested with an assistive technology to verify that the changes to the associated element are recognized.

Expected Results

• Step #3 and #5 are true.

The objective of this technique is to illustrate the use of both keyboard-specific and mouse-specific events with code that has a scripting function associated with an event. Using both keyboard-specific and mouse-specific events together ensures that content can be operated by a wide range of devices. For example, a script may perform the same action when a keypress is detected that is performed when a mouse button is clicked. This technique goes beyond the SC requirement for keyboard access by including not only keyboard access but access using other devices as well.

In JavaScript, commonly used event handlers include, onblur, onchange, onclick, ondblclick, onfocus, onkeydown, onkeypress, onkeyup, onload, onmousedown, onmousemove, onmouseout, onmouseover, onmouseup, onreset, onselect, onsubmit, onunload. Some mouse-specific functions have a logical corresponding keyboard-specific function (such as 'onmouseover' and 'onfocus'). The keyboard event handler should be provided, that executes the same function as the mouse event handler.

The following table suggests keyboard event handlers to pair mouse event handlers.

¹ Although click is in principle a mouse event handler, most HTML user agents process this event when the control is activated, regardless of whether it was activated with the mouse or the keyboard. In practice, therefore, it is not necessary to duplicate this event. It is included here for completeness since non-HTML user agents do have this issue.

² Since the keypress event handler reacts to any key, the event handler function should check first to ensure the Enter key was pressed before proceeding to handle the event. Otherwise, the event handler will run each time the user presses any key, even the tab key to leave the control, and this is usually not desirable.

Some mouse-specific functions (such as dblclick and mousemove) do not have a corresponding keyboard-specific function. This means that some functions may need to be implemented differently for each device (for example, including a series of buttons to execute, via keyboard, the equivalent mouse-specific functions implemented).

• Overview of Creating Accessible JavaScript

• Providing keyboard-controllable event handlers

Procedure

1. Find all interactive functionality

2. Check that all interactive functionality can be accessed using the keyboard alone

Expected Results

• #2 is true

The objective of this technique is to demonstrate how to use functions of the Document Object Model (DOM) to add content to a page instead of using document.write or object.innerHTML. The document.write() method does not work with XHTML when served with the correct MIME type (application/xhtml+xml), and the innerHTML property is not part of the DOM specification and thus should be avoided. If the DOM functions are used to add the content, user agents can access the DOM to retrieve the content. The createElement() function can be used to create elements within the DOM. The createTextNode() is used to create text associated with elements. The appendChild(), removeChild(), insertBefore() and replaceChild() functions are used to add and remove elements and nodes. Other DOM functions are used to assign attributes to the created elements.

• HTML 4.01 The Document Object Model, More methods from Webreference.com

(none currently listed)

Procedure

For pages that dynamically create new content:

1. Examine the source code and check that the new content is not created using document.write(), innerHTML, outerHTML, innerText or outerText.

Expected Results

• Check #1 is true.

The objective of this technique is to control blinking with script so it can be set to stop in less than three seconds by the script. Script is used to start the blinking effect of content, control the toggle between visible and hidden states, and also stop the effect at three seconds or less. The setTimeout() function can be used to toggle blinking content between visible and hidden states, and stop when the number of iterations by the time between them adds up to nearly three seconds.

Procedure

For each instance of blinking content:

1. Start a timer for 3 seconds at the start of the blink effect.

2. When the timer expires, determine if the blinking has stopped.

Expected Results

• For each instance of blinking content, #2 is true.

The objective of this technique is to avoid confusion that may be caused by the appearance of new windows that were not requested by the user. Suddenly opening new windows can disorientate or be missed completely by some users. If the document type does not allow the target attribute (it does not exist in HTML 4.01 Strict or XHTML 1.0 Strict) or if the developer prefers not to use it, new windows can be opened with ECMAScript. The example below demonstrates how to open new windows with script: it adds an event handler to a link (a element) and warns the user that the content will open in a new window.

• Ensuring that all id attribute values are unique for the document AND that the Web unit is well-formed

Procedure

1. Activate each link in the document to check if it opens a new window.

2. For each link that opens a new window, check that it uses script.

Expected Results

• #2 is true.

The objective of this technique is to demonstrate how visual appearance may be enhanced via style sheets while still maintaining a meaningful presentation when style sheets are not applied. Using the positioning properties of CSS2, content may be displayed at any position on the user's viewport. Using structural elements ensures that the meaning of the content can still be determined when styling is not available.

• CSS-Discuss Home Page

• CSS-Discuss on CSS Layouts

• Failure of SC 1.3.3 due to changing the meaning of content by positioning information with CSS

Procedure

For content which uses CSS for positioning

1. Remove the style information from the document or turn off use of style sheets in the user agent.

2. Check that the structural relations and the meaning of the content are preserved.

Expected Results

• Check #2 is true.

The objective of this technique is to provide a mechanism to add purely decorative images and images used for visual formatting to Web content without requiring additional markup within the content. This makes it possible for assistive technologies to ignore the non-text content. Some user agents can ignore or turn off CSS at the user's request, so that background images included with CSS simply "disappear" and do not interfere with display settings such as enlarged fonts or high contrast settings.

Background images can be included with the following CSS properties:

• background,

• background-image,

• content, combined with the :before and :after pseudo-elements,

• list-style-image.

Note: This technique is not appropriate for any image that conveys information or provides functionality, or for any image primarily intended to create a specific sensory experience.

• The background property in the CSS 2.0 specification

• The HTML 4.01 specification states that the background attribute of the body element is deprecated

• Failure of SC 1.1.1 due to using CSS to include images that convey important information

Procedure

1. Check for the presence of decorative images

2. Check that they are included with CSS

Expected Results

• If #1 is true, then #2 is true.

The objective of this technique is to supplement the link text by adding additional text that describes the unique function of the link but styling the additional text so that it is not rendered on the screen by user agents that support CSS. When information in the surrounding context is needed to interpret the displayed link text, this technique provides a complete description of the link unique function while permitting the less complete text to be displayed.

This technique works by creating a CSS selector to target text that is to be hidden. The rule-set for the selector places the text to be hidden in a 1-pixel box with overflow hidden, and positions the text outside of the viewport. This ensures the text does not display on screen but remains accessible to assistive technologies such as screen readers and braille displays. Note that the technique does not use visibility:hidden or display:none properties, since these can have the unintentional effect of hiding the text from assistive technology in addition to preventing on-screen display.

No resources available for this technique.

• Supplementing link text with the title attribute
• Providing link text that describes the purpose of a link
• Providing link text that describes the purpose of a link for anchor elements

Procedure

For each anchor element using this technique:

1. Check that an element has been defined that confines its display to a pixel and positions text outside the display with overflow hidden

2. Check that the element of that class is included in the content of the anchor

3. Check that the combined content of the anchor describes the purpose of the link

Expected Results

• All checks above are true.

The objective of this technique is to demonstrate how the visual appearance of spacing in text may be enhanced via style sheets while still maintaining meaningful text sequencing. The CSS letter-spacing property helps developers control the amount of white space between characters. This is recommended over adding blank characters to control the spacing, since the blank characters can change the meaning and pronunciation of the word.

• CSS 2.0: Letter and word spacing

• Failure of SC 1.3.3 due to changing the meaning of content by positioning information with CSS
• Failure of SC 1.3.3 due to using white space characters to control spacing within a word

Procedure

For each word that appears to have non-standard spacing between characters:

1. Check whether the CSS letter-spacing property was used to control spacing.

Expected Results

• Check #1 is true.

The objective of this technique is to provide a mechanism to bypass blocks of material that are repeated on multiple Web units. The first interactive item in the Web unit is a link to the beginning of the main content. Activating the link sets focus beyond the other content to the main content.

• Skip Navigation Links Jim Thatcher

(none currently listed)

Procedure

1. Check that a link is the first focusable control on the Web unit.

2. Check that the description of the link communicates that it links to the main content.

3. Check that activating the link moves the focus to the main content.

4. Check that after activating the link, the keyboard focus has moved to the main content

Expected Results

• All checks above are true.

The objective of this technique is to provide a way to pause movement or scrolling of content. If the user needs to pause the movement, to reduce distraction or to have time to read it, they can do so, and then restart it as needed. This mechanism can be provided either through interactive controls that conform to WCAG or through keyboard shortcuts. If keyboard shortcuts are used, they are documented.

Procedure

On a page with moving or scrolling content,

1. Use the mechanism provided in the Web unit or by the user agent to pause the moving or scrolling content.

2. Check that the moving or scrolling has stopped and does not restart by itself.

3. Use the mechanism provided to restart the moving content.

4. Check that the movement or scrolling has resumed from the point where it was stopped.

Expected Results

• #2 and #4 are true.

The objective of this technique is to provide users with all the time they need to complete an activity. This technique involves providing a specified activity which does not require timed interaction. Users are allowed as much time as they need to interact with the activity.

• Resource-Oriented vs. Activity-Oriented Web Services

• Top Ten Web Design Mistakes of 2005

Procedure

1. Determine if any timed interactions are present.

Expected Results

• #1 is false.

The objective of this technique is to ensure that all Web pages have titles associated with them that define in a simple phrase the purpose of the Web page. This helps users to orient themselves quickly within a set of Web pages without having to search for orientation information in the content of the Web pages themselves.

No resources available for this technique.

• Providing a title using the title element

Procedure

1. Examine each Web page in the set

2. Check whether each Web page is associated with a title

Expected Results

• #2 is true.

The objective of this technique is to all additional audio description to be inserted into a multimedia presentation when there is not enough time in the gaps int the dialog. This is done by simply freezing the image so that additional audio description of the video can be played. When the description is finished, the multimedia continues.

This technique provides people who are blind or who otherwise would miss information presented visually with additional audio description beyond that which can be provided by standard audio descriptions. Often the gaps in dialog are insufficient to allow enough audio description to be inserted to cover all the important visual information being presented. This technique freezes the multimedia presentation to allow additional audio description to be played. The multimedia presentation is then resumed.

Because it disrupts viewing for those who do not need the additional description, techniques that allow you to turn the feature on and off are often provided. Alternately, versions with and without the additional description can be provided.

• Providing audio descriptions in SMIL 1.0
• Adding extended audio descriptions in SMIL 2.0

Procedure

1. Play multimedia with extended audio description enabled

2. Check to see if multimedia freezes from time to time to allow audio description to convey important information regarding visual content

Expected Results

• #2 is true

The objective of this technique is to allow users who cannot hear to be able to access real-time multimedia broadcasts. It is more difficult to create accurate real-time captions because there is little time to correct mistakes or to listen a second time or consult someone to be sure the words are accurately reproduced. It is also harder to simplify or paraphrase information if it is flowing too quickly.

Real-time typing text entry techniques exist using stenographic and rapid typing technologies. Re-voicing speech-to-text (where a person listens to speech and then carefully re-voices it into a computer trained to their speech) is used today for telephone relay services and may be used in the future for captioning. Eventually speech-to-text with correction will be possible.

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• Providing open captions that are embedded directly in the video stream
• Providing closed captions

Procedure

1. a procedure and policy are in place to ensure that captions are delivered in real-time

Expected Results

• #1 is true

The objective of this technique is to allow assistive technology to understand Web content so that it can convey equivalent information to the user through an alternate user interface.

Sometimes content is not created using markup language but rather using a programming language or tools. In many cases, these technologies have interface components that are already programmed to interface with accessibility APIs. If and author uses these components and fills in the properties (e.g. name, etc) the resulting user interface components in the content will be accessible to assistive technology.

However, if an author wants to create a user interface component that is new and they cannot use standard components, then they need to be sure to add the accessibility provisions themselves - and implement them in a way that is compatible with the accessibility API.

(none currently listed)

Procedure

1. Render content using an accessible User Agent

2. Use an Accessibility Tool designed for the Accessibility API of the User agent to evaluate each user interface component

3. Check that name and role for each user interface component is found by the tool.

4. Change the values on the component

5. Check that the Accessibility tool is alerted.

Expected Results

• Step #3 and #5 are true for each user interface component

The objective of this technique is to minimize the distraction caused by blinking content and enable users to re-focus on the other content on the page.

Blinking content can be created using a variety of technologies, many of which include options to loop blinking content continuously or to otherwise specify the amount of time the blinking content is displayed. Limiting the blinking of content to three seconds minimizes the distraction that blinking can cause. This will benefit people with certain types of learning disabilities and people with low vision.

Procedure

1. Find all items that blink.

2. For each item that blinks, determine if the interval between the start and end of the blinking is less than three seconds.

Expected Results

• #2 is true.

The objective of this technique is to provide information to users about what will happen when a change to a form control results in a change of context. Because changing the value of a form control does not typically result in a change of context, it is important that authors provide instructions that make the user aware of the behavior in advance. Where possible, it is a good idea to programmatically associate the instructions describing the change with the form control itself.

(none currently listed)

Procedure

• locate content where changing the setting of a form control results in a change of context

• check to see that an explanation of what will happen when the control is changed is available prior to the controls activation

Expected Results

• #2 is true.

The objective of this technique is to ensure that when color is used to convey information, such as required form fields, the information conveyed by the color is also conveyed explicitly in text.

No resources available for this technique.

(none currently listed)

Procedure

For each item where color is used to convey information:

1. Check that the information conveyed is also available in text and that the text is not conditional content.

Expected Results

• Check #1 is true.

The purpose of this technique is to allow people who have photosensitive seizures to view Web sites without encountering material that is likely to cause a seizure. Warnings can be provided but people may miss them and children may not be able to read or understand them. With this technique all material is checked and if it violates flash or red flash thresholds it is either not put on the site or it is modified so that it does not violate the thresholds.

• Harding FPA Web Site

• Trace Center Photosensitive Epilepsy Analysis Tool (PEAT)

(none currently listed)

Procedure

1. Check to see if content violates the flash and/or red flash thresholds by either

   • visually checking that there are no more than 2 flashes of any kind in a row OR

   • using a tool that will check for General Flash or Red Flash thresholds automatically

Expected Results

• Step 1 is false

The objective of this technique is to make sure that users can read text that is presented over a background. This technique goes beyond the 5:1 contrast technique to provide a higher level of contrast to make it easier for people with low vision to read.

If the background is a solid color (or all black or all white) then the luminosity contrast of the text can be maintained by making sure that each of the text letters have 10:1 luminosity contrast with the background.

If the background or the letters vary in luminosity (or are patterned) then the background around the letters can be chosen or shaded so that the letters maintain 10:1 luminosity contrast with the background behind them even if they do not have that luminosity contrast with the entire background.

The luminosity contrast can sometimes be maintained by changing the luminosity of the letters as the luminosity of the background changes across the page.

Another method is to provide a halo around the text that provides the necessary luminosity contrast if the background image or color would not normally be sufficiently different in luminosity.

• Luminosity Contrast Analyser – Application

• Luminosity Contrast Ratio Analyser - online service

• Colour Contrast Analyser - Firefox Extension

(none currently listed)

Procedure

1. Measure the luminosity of each letter (unless they are all uniform) using the formula:

   • Luminosity = 0.2126 * ((R / FS) ^ 2.2) + 0.7152 * ((G / FS) ^ 2.2) + 0.0722 * ((B / FS) ^ 2.2)

   • where R, G, and B are the Red, Green, and Blue RGB values of the color, and FS is the maximum possible full scale RGB value for R, G, and B (255 for eight bit color channels).

   • For aliased letters use luminosity two pixels in from the edge of the letter.

   Measure the luminosity of the background pixels immediately next to the letter using same formula.

2. Calculate the luminosity contrast ratio using the following formula.

   • Luminosity Contrast Ratio = (L1+.05) / (L2+.05).

   • where L1 is the higher value (of text or background) and L2 is the lower value.

   Check that the luminosity contrast ratio is equal to or greater than 10:1

Expected Results

• #4 is true

The objective of this technique is to make sure that users can read text that is presented over a background. This technique uses a lower threshold for contrast to allow more flexibility by authors in color choices.

If the background is a solid color (or all black or all white) then the luminosity contrast of the text can be maintained by making sure that each of the text letters have 5:1 luminosity contrast with the background.

If the background or the letters vary in luminosity (or are patterned) then the background around the letters can be chosen or shaded so that the letters maintain 5:1 luminosity contrast with the background behind them even if they do not have that luminosity contrast with the entire background.

The luminosity contrast can sometimes be maintained by changing the luminosity of the letters as the luminosity of the background changes across the page.

Another method is to provide a halo around the text that provides the necessary luminosity contrast if the background image or color would not normally be sufficiently different in luminosity.

• Luminosity Contrast Analyser – Application

• Luminosity Contrast Ratio Analyser - online service

• Colour Contrast Analyser - Firefox Extension

(none currently listed)

Procedure

1. Measure the luminosity of each letter (unless they are all uniform) using the formula:

   • Luminosity = 0.2126 * ((R / FS) ^ 2.2) + 0.7152 * ((G / FS) ^ 2.2) + 0.0722 * ((B / FS) ^ 2.2)

   • where R, G, and B are the Red, Green, and Blue RGB values of the color, and FS is the maximum possible full scale RGB value for R, G, and B (255 for eight bit color channels).

   • For aliased letters use luminosity two pixels in from the edge of the letter.

   Measure the luminosity of the background pixels immediately next to the letter using same formula.

2. Calculate the luminosity contrast ratio using the following formula.

   • Luminosity Contrast Ratio = (L1+.05) / (L2+.05).

   • where L1 is the higher value (of text or background) and L2 is the lower value.

   Check that the luminosity contrast ratio is equal to or greater than 5:1

Expected Results

The luminosity contrast ratio is equal to or greater than 5:1

• #4 is true

The objective of this technique is to avoid flashing at rates that are known to cause seizures if the flashes are bright and large enough. Since some users may be using screen enlargers, this technique limits the flashing of any size content to no more than three flashes in any 1-second period.

Examples of 3.5 flashes or 7 transitions:

• STARTING DARK-LIGHT-DARK-LIGHT-DARK-LIGHT-DARK-LIGHT or

• STARTING LIGHT-DARK-LIGHT-DARK-LIGHT-DARK-LIGHT-DARK.

• Trace Center Photosensitive Epilepsy Analysis Tool (PEAT)

• Ensuring that content does not violate the general flash threshold or red flash threshold

Procedure

1. Check that there are no more than three flashes during any 1-second period.

2. If there are three flashes, check that the Light/Dark status at the end of the 1 second period is the same as at the start.

Expected Results

• Both Step one and Step 2 are true.

The objective of this technique is to ensure that users can always access an accessible version of the content. When content is provided in a format that does not conform to WCAG, the site as a whole can still conform if alternate versions of the inaccessible content are provided. The success criterion requires that alternate versions are available "from the same URI" as the nonconforming version. It is the intent of that wording that it can be sufficient to provide a link to conforming content from the nonconforming content (see Providing a link at the top of the nonconforming content that points to an alternate version that does meet WCAG 2.0 Level 1 success criteria (future link)).

In order for the link to alternate content to fulfill its intent, the link needs to conform to WCAG requirements, that is, be accessible. In some technologies, even though the content as a whole may not conform, a link can be provided that does conform. In other technologies, however, it is not even possible to provide a link to alternate content within that technology that conforms. Users may be unable to find the alternate content if the only pointer is in an inaccessible technology.

This technique describes how to provide alternate content in such a situation. In this technique, the WCAG conforming version contains a link to the nonconforming version. This way users access the conforming content, and only access the nonconforming content if they wish, via a link. In order to ensure users do not accidentally get "stuck" in inaccessible content, the nonconforming version is excluded from search engine results, site maps (unless the conforming version is also included), etc.

• Providing a link at the beginning of the nonconforming content that points to an alternate version that does meet WCAG 2.0 Level 1 success criteria

Procedure

Where WCAG conforming alternatives are provided for nonconforming content:

1. Check that there is a link to the nonconforming content from the conforming content.

2. Check that the nonconforming content does not appear in search engine results, site maps, and the site's regular navigation.

Expected Results

• #1 and #2 are true.

The objective of this technique is to ensure that keyboard users do not become trapped in a subset of the content that can only be exited using a mouse or pointing device. A common example is content rendered by plug-ins. Plug-ins are user agents that render content inside the user agent host window and respond to all user actions that takes place while the plug-in has the focus. If the plug-in does not provide a keyboard mechanism to return focus to the parent window, users who must use the keyboard may become trapped in the plug-in content.

This problem can be avoided by using one of the following mechanisms to provide a way for users to escape the subset of the content:

• Ensuring that the keyboard function for advancing focus within content (commonly the tab key) exits the subset of the content after it reaches the final navigation location.

• Providing a keyboard function to move the focus out of the subset of the content. Be sure to document the feature in an accessible manner within the subset.

• If the subset of the content does natively provide a "move to parent" keyboard command, documenting that command before the user enters the plug-in so they know how to get out again.

No resources available for this technique.

(none currently listed)

Procedure

1. tab through content from start to finish.

2. check to see if keyboard focus is trapped in any of the content such that the person cannot move out of any part of the content and continue through the rest of the content.

Expected Results

• #2 is false

The objective of this technique is to identify the purpose of a link from the link and its context. This is done by associating the link with its text and with text that is associated with the immediately enclosing structural unit of the content. The purpose of the link is identified by interpreting the link in the context of the text associated with its enclosing structure unit. The description lets a user distinguish this link from links in the Web unit that lead to other destinations and helps the user determine whether to follow the link. The URI of the destination is generally not sufficiently descriptive.

Note that only the text associated with the immediately enclosing structural unit of the link is used to provide the context for the link. The definition of the immediately enclosing structural unit is technology-specific. It may not be possible to represent complex content in a way that includes all the necessary context for a link in this unit, but still represent other important relationships in the content. In this situation, another technique must be used to identify the purpose of the link.

No resources available for this technique.

• Identifying the purpose of a link using link text and text associated with the parent element of the link

Procedure

For each link in the content that uses this technique:

1. Check that text of the link combined with the text associated with the enclosing structural unit of content describes the purpose of the link

Expected Results

• The above check is true.

The objective of this technique is to allow users who cannot hear or read text rapidly to be able to access multimedia material.

For those who communicate primarily in sign language it is sometimes less preferable and sometimes not possible for them to read and understand text at the rate it is presented in captions. For these latter individuals it is important to provide sign language presentation of the audio information.

One universally compatible way of doing this is to simply embed a video of the sign language interpreter in the corner of the video stream. This has the disadvantage of providing a lower resolution image that cannot be easily enlarged without enlarging the entire image.

• Guidelines for the Production of Signing Books

  • "Sign Language presentation" gives a broad overview of issues to consider when filming sign language interpreters. Includes discussion of signing both written and spoken originals.

  • Techniques for filming are discussed in chapter 12, “Filming the Signer(s)”.

  • Useful information about how to display the sign language interpreter in relation to the original multimedia content is provided in Chapter 13, "Editing"

    Note: These techniques may need to be adapted for Web-based presentation.

(none currently listed)

Procedure

1. Have someone watch the program who can hear and is familiar with the sign language being used.

2. Check to see if there is a sign language interpreter on screen.

3. Check to see that dialog and important sounds are being conveyed by the interpreter visible on screen.

Expected Results

• #2 and #3 are true

The objective of this technique is to make the definition of a word, phrase, or abbreviation available by providing the definition, either within the same Web unit or in a different Web unit, and establishing a link between the item and its definition.

Links are a powerful option for providing access to the definition of a word, phrase, or abbreviation. A user can use the link to find the definition quickly and easily, and then return to his place in the content via the user agent's Back button.

No resources available for this technique.

(none currently listed)

Procedure

For each word, phrase, or abbreviation to be defined:

1. Check that at least the first instance of the item is a link.

2. Check that each link navigates to the definition of the item.

Expected Results

• The checks above all pass.

The objective of this technique is to allow authors to include sound behind speech without making it too hard for people with hearing problems to understand the speech. Making sure that the speech is 20 db louder than the backgound sound makes the speech 4 times louder than the background sounds. For information on Decibels (dB) see About Decibels

• About Decibels by Gregg Vanderheiden

(none currently listed)

Procedure

1. Locate loud values of background content between forground speech

2. Measure the volume in dB(A) SPL

3. Measure the volume of the forground speech in dB(A) SPL

4. Subtract the values

5. Check that the result is 20 or greater.

Expected Results

• #5 is true

The objective of this technique is to ensure that the order of content presented to assistive technologies allows the user to make sense of the content. Some techniques permit the content to be rendered visually in a meaningful sequence even if the underlying order of the content is confusing.

For example, when mixing languages with different directionality in HTML, the bidirectional algorithm may place punctuation in the wrong place. Correctly ordered content maintains the punctuation in the correct sequence in the content stream and uses markup to override the bidirectional algorithm, rather than moving the punctuation in the content stream so that the default rendering positions it correctly.

When rendered visually, white space characters such a space or tab may not appear to be part of the content. However, when inserted into the content to control visual formatting, they may interfere with the meaning of the content.

At a larger granularity, controlling the placement of blocks of content in an HTML document using layout tables may produce a rendering in which related information is positioned together visually, but separated in the content stream. Since layout tables are read row by row, if the caption of an illustration is placed in the row following the illustration, it may be impossible to associate the caption with the image.

No resources available for this technique.

• Failure of SC 1.3.3 due to changing the meaning of content by positioning information with CSS
• Failure of SC 1.3.3 due to changing the meaning of content by positioning information with HTML layout tables

Procedure

1. Identify meaningful sequences in the source document.

2. Check that the elements of each meaningful sequence are in consecutive order in the content.

Expected Results

• Check #2 is true.

With this technique, a link to the collated document of captions and audio descriptions is provided. The collated document could be at another location on the same Web unit or at another URI. A link to the collated document is immediately adjacent to the non-text content. The link can be immediately before or after the multimedia content. If the collated document is on the same Web unit as other content then put "End of document" at the end so that they know when to stop reading and return to their previous place. If a "Back" button will not take the person back to the point from which they jumped, then a link back to the non-text content location is provided.

No resources available for this technique.

(none currently listed)

Procedure

1. Check for the presence of a link immediately before or after the non-text content

2. Check that it is a valid link that points directly to the collated document of this particular multimedia.

3. Check for the availability of a link or back function to get the user back to the original location of the multimedia content

Expected Results

• Items #1 through 3 are all true.

The objective of this technique is to ensure that interactive elements receive focus in an order that follows sequences and relationships in the content. When designing the content, the interactive elements such as links and form controls are placed in the content so that the default tab order follows the sequences and relationships in the content. Each technology defines its default tab order, so the mechanism for placing the controls in the content will depend on the technology used.

As an example, in HTML, the default focus order follows the order in which elements appear in the content source. When the order of the HTML source matches the visual order of the Web unit, tabbing through the content follows the visual layout of the content. When the source order does not match the visual order, the tab order through the content must reflect the logical relationships in the content that are displayed visually.

No resources available for this technique.

• Ordering the content in a meaningful sequence

Procedure

1. Determine the order of interactive elements in the content.

2. Determine the logical order of interactive elements.

3. Check that the order of the interactive elements in the content is the same as the logical order.

Expected Results

• Check #3 is true.

The purpose of this technique is to allow authors to play a sound on their page but avoid the problem of users not being able to use their screen readers due to interference by the content sound. It also allows the author to avoid putting controls on the page to control the sound - and the problem faced by consumers with screen readers in finding the control (when unable to hear their screen reader).

The technique is simple. The sound plays for 3 or less seconds and stops automatically.

(none)

(none currently listed)

Procedure

1. open the URI

2. check that all sound that plays automatically stops in 3 seconds or less

Expected Results

• #2 is true

The objective of this technique is to make content easier to use by making the placement of repeated components more predictable. This technique helps maintain consistent layout or presentation between Web units by presenting components that are repeated in these Web units in the same relative order each time they appear. Other components can be inserted between them, but their relative order is not changed.

This technique also applies to navigational components that are repeated. Web units often contain a navigation menu or other navigational component that allows the user to jump to other Web units. This technique makes the placement of navigational components more predictable by presenting the links or programmatic references inside a navigational component in the same relative order each time the navigational component is repeated. Other links can be removed or inserted between the existing ones, for example to allow navigation inside a subsection of a set of Web units, but the relative order is not changed.

(none currently listed)

Procedure

1. List components that are repeated on each Web unit in a set of Web units (for example, on each page in a Web site).

2. For each component, check that it appears in the same relative order with regard to other repeated components on each Web unit where it appears.

3. For each navigational component, check that the links or programmatic references are always in the same relative order.

Expected Results

• #2 is true.

• #3 is true.

The objective of this technique is to make the definition of a word, phrase, or abbreviation available by providing the definition in a glossary. A glossary is an alphabetical list of words, phrases, and abbreviations with their definitions. Glossaries are most appropriate when the words, phrases, and abbreviations used within the content relate to a specific discipline or technology area.

The glossary is included at the end of the Web unit or the glossary is located via one of the mechanisms for locating content within a set of Web units. (See How to Meet Success Criterion 2.4.2.)

If the glossary contains several definitions for the same word, phrase, or abbreviation, simply providing the glossary is not sufficient to satisfy this success criterion. A different technique should be used to find the correct definition. This is especially important if the uses of the word, phrase, or abbreviation are not unique within the Web unit, that is, if different occurrences of the item have different definitions.

No resources available for this technique.

(none currently listed)

Procedure

Check that either

1. The glossary is included in the Web unit, or

2. A mechanism is available to locate the glossary.

For each word, phrase, or abbreviation to be defined,

1. Check that the item is defined in the glossary, and

2. Check that the glossary contains only one definition for each item.

Expected Results

• All checks above pass.

A site map is a Web page that provides links to different sections of the site. To make the site map available within the site, at a minimum every page that is listed in the site map contains a link to the site map.

The site map serves several purposes.

• It provides an overview of the entire site.

• It helps users understand what the site contains and how the content is organized.

• It offers an alternative to complex navigation bars that may be different at different parts of the site.

There are different types of site maps. The simplest and most common kind of site map is an outline that shows links to each section or sub-site. Such outline views do not show more complex relationships within the site, such as links between pages in different sections of the site. The site maps for some large sites use headings that expand to show additional detail about each section.

A site map describes the contents and organization of a site. It is important that site maps be updated whenever the site is updated. A Web page that does not link to all the sections of a site, that presents an organization that is different from the site's organization, or that contains links that are no longer valid is not a valid site map.

• Graphic Organizers page at the National Center for Accessible Curriculum provides a useful overview of different kinds of graphic organizers and their uses, plus a summary of relevant research on the effectiveness of graphical organizers for students with learning disabilities.

• Usability Glossary: sitemap

Procedure

1. Check that the site contains a site map

2. Check that the links in the site map lead to the corresponding sections of the site

3. For each link in the site map, check that the target page contains a link to the site map

4. For each page in the site, check that the page can be reached by following some set of links that start at the site map.

Expected Results

• All of the checks above are true.

A table of contents provides links to section headings and sub-headings within the hierarchical structure of a document.

The table of contents serves two purposes:

• It gives users an overview of the document's contents and organization.

• It allows readers to go directly to a specific section of an on-line document.

The table of contents typically includes only major sections of the document, though in some cases an expanded table of contents that provides a more detailed view of a complex document may be desirable.

No resources available for this technique.

(none currently listed)

Procedure

1. Check that a Table of Contents or a link to a Table of Contents exists in the document.

2. Check that the values and order of the entries in the Table of Contents correspond to the names and order of the sections of the document.

3. Check that the entries in the Table of Contents link to the correct sections of the document.

Expected Results

• All checks above are true.

A breadcrumb trail helps the user to visualize how content has been structured and how to navigate back to previous Web units, and may identify the current location within a series of Web units. A breadcrumb trail either displays locations in the path the user took to reach the Web unit, or it displays the location of the current Web unit within the organization of the site.

Breadcrumb trails are implemented using links to the Web units that have been accessed in the process of navigating to the current Web unit. They are placed in the same location within each Web unit in the set.

It can be helpful to users to separate the items in the breakcrumb trailing with a visible separator. Examples of separators include >, |, /, and ::.

No resources available for this technique.

(none currently listed)

Procedure

When breadcrumb trails have been implemented in a set of Web units:

1. Navigate to a Web unit .

2. Check that a breadcrumb trail is displayed.

3. Check that the breadcrumb trail displays the correct navigational sequence to reach the current location or the correct hierarchical path to the current location within the site structure.

4. For a breadcrumb trail that does not include the current location:

   1. Check that all elements in the breadcrumb trail are implemented as links.

5. For a breadcrumb trail that does include the current location:

   1. Check that all elements except for the current location are implemented as links.

   2. Check that the current location is not implemented as a link.

6. Check that all links navigate to the correct Web unit as specified by the breadcrumb trail.

Expected Results

• For all Web units in the set using breadcrumb trails,

  • Checks #2, #3, and #6 are true.

  • Either check #4 or #5 is true.

This technique provides a descriptive label for Live audio-only and live video-only content. This label may be used in combination with a full text transcript of the audio or a full text or audio description of the video. Those alternative however are not part of this technique. The purpose of this technique is to ensure that the user can determine what the non-text content is - even if they cannot access it. NOTE: Even if full alternatives are also available, it is important that users be able to identify the non-text content when they encounter it so that they are not confused, and so that they can associate it with the full alternative when they encounter it.

(none currently listed)

Procedure

1. remove, hide, or mask the non-text content

2. display the text alternative(s)

3. check that the purpose of the non-text content is clear - even if content is lost.

Expected Results

• #3 is true.

The purpose of this technique is to provide an accessible alternative way of presenting the information in a multimedia presentation.

In a multimedia presentation, information is presented in a variety of ways including

• dialogue,

• sounds (natural and artificial),

• the setting and background,

• the actions and expressions of people, animals, etc.,

• text or graphics,

• and more.

In order to present the same information in accessible form, this technique involves creating a document that tells the same story and presents the same information as the multimedia. Such a document is sometimes called a screenplay. It includes all the important dialogue and actions as well as descriptions of backgrounds etc. that are part of the story.

If an actual screenplay was used to create the multimedia in the first place, this can be a good place to start. In production and editing however, the multimedia usually changes from the screenplay. For this technique, the original screenplay would be corrected to match the dialogue and what actually happens in the final edited form of the multimedia.

In addition, some special types of multimedia include interaction that has to occur at particular places in the playing of the multimedia. Sometimes it may result in an action taking place (e.g. something is purchased, sent, done, etc.). Sometimes it may change the course of the multimedia (e.g. the multimedia has multiple paths that are determined by user input). In those cases links or some other mechanism would be used in the full multimedia text alternative to allow people using the alternative to be able to have the same options and abilities as those using the multimedia.

No resources available for this technique.

• Creating an extended audio description for the multimedia content

Procedure

1. View the multimedia presentation with the full multimedia text alternative in hand.

2. Check that the dialogue in the full multimedia text alternative matches the dialogue in the multimedia presentation

3. Check that full multimedia text alternative has descriptions of sounds.

4. Check that full multimedia text alternative has descriptions of setting and setting changes.

5. Check that full multimedia text alternative has descriptions of actions and expressions of any 'actors' (people, animals etc).

Expected Results

• #2, 3, 4, 5 are true.

The objective of this technique is to provide the definition of words, phrases, jargon, or abbreviation expansions by adding a mechanism to access an on-line dictionary to the Web unit. This technique uses existing resources on the Web to provide the definition rather than requiring the author to create a glossary or other mechanism within the site. By providing access from within the Web unit, a user can easily locate the desired definition.

No resources available for this technique.

• Using inline definitions
• Linking to definitions

Procedure

For each word, phrase, or abbreviation to be defined:

1. Check that a mechanism exists within the Web unit to search for the word, phrase, or abbreviation via an on-line dictionary.

2. Check that a search of the dictionary for the word, phrase, or abbreviation finds the correct definition.

Expected Results

• Checks #1 and #2 are true.

The objective of this technique is to provide context sensitive help for users as they enter data in forms by providing at least one link to the help information on each Web unit. The link targets a help page with information specific to that Web unit. Another approach is to provide a help link for every interactive control. Positioning this link immediately before or after the control allows users to easily tab to it if they have problems in the control. Displaying the help information in a new browser window ensures that any data that has already been entered into the form will not be lost. NOTE: A link is not the only means to provide help.

Procedure

1. Identify a Web unit that contains forms.

2. Determine if there is at least one link to help information specific to completing the form on this Web unit or other resource.

3. Determine if there are links either before or after each interactive control to help information specific to that control.

Expected Results

• Either #2 or #3 are true.

The objective of this technique is to provide a way to link to remote long descriptions in technologies that do not have a long description feature built directly into them (e.g. longdesc) or where the feature is known to not be supported.

With this technique, the long description is provided in another location than the non-text content. This could be at another location within the same URI or at another URI. A link to that long description is provided that is immediately adjacent to the non-text content. The link can be immediately before or after the non-text content. If the description is located along with other text then put "End of description" at the end so that they know when to stop reading and return to the main content. If a "Back" button will not take the person back to the point from which they jumped, then a link back to the non-text content location is provided.

This technique was commonly used in HTML before 'longdesc' was added to the specification. In HTML it was called a D-Link because it was usually implemented b