• A captioned tutorialA video clip shows how to tie a knot. The captions read,”(music)Using rope to tie knots was an important skill for the likes of sailors, soldiers and woodsmen..”From Sample Transcript Formatting by Whit Anderson.
• A complex legal document contains synchronized media clips for different paragraphs that show a person speaking the contents of the paragraph. Each clip is associated with its corresponding paragraph. No captions are provided for the synchronized media.
• An instruction manual containing a description of a part and its necessary orientation is accompanied by a synchronized media clip showing the part in its correct orientation. No captions are provided for the synchronized media clip.
• An orchestra provides captions for videos of performances. In addition to capturing dialog and lyrics verbatim, captions identify non-vocal music by title, movement, composer, and any information that will help the user comprehend the nature of the audio. For instance captions read,”[Orchestral Suite No. 3.2 in D major, BWV 1068, Air]
  [Johann Sebastian Bach, Composer]♪ Calm melody with a slow tempo ♪”

The purpose of this guideline is to ensure that all information is available in a form that can be perceived by all users, for example, spoken aloud, or presented in a simpler visual layout. If all of the information is available in a form that can be determined by software, then it can be presented to users in different ways (visually, audibly, tactilely etc.). If information is embedded in a particular presentation in such a way that the structure and information cannot be programmatically determined by the assistive technology, then it cannot be rendered in other formats as needed by the user.

The Success Criteria under this guideline all seek to ensure that different types of information that are often encoded in presentation are also available so that they can be presented in other modalities.

• structure: the way the parts of a Web page are organized in relation to each other; and the way a collection of Web pages is organized
• presentation: rendering of the content in a form that can be perceived by users

• Example 1: A drawing Program.

A drawing program allows users to create, size, position and rotate objects from the keyboard.

• Example 2: A drag and Drop Feature.

An application that uses drag and drop also supports “cut” and “paste” or form controls to move objects.

• Example 3: Moving between and connecting discrete points.

A connect-the-dots program allows the user to move between dots on a screen and use the spacebar to connect the current dot to the previous one.

• Example 4: Exception – Painting Program.

A watercolor painting program passes as an exception because the brush strokes vary depending on the speed and duration of the movements.

• Example 5: Exception – Model helicopter flight training simulator.

A model helicopter flight training simulator passes as an exception because the nature of the simulator is to teach real-time behavior of a model helicopter.

• Example 6: A PDA with an optional keyboard

A PDA device that is usually operated via a stylus has an optional keyboard that can be attached. The keyboard allows full Web browsing in standard fashion. The Web content is operable because it was designed to work with keyboard-only access.

• • A Web site uses a client side time limit to help protect users who may step away from their computer. After a period of inactivity the Web page asks if the user needs more time. If it doesn’t get a response – it times out.
  • A Web page has a field that automatically updates with the latest headlines in a rotating fashion. There is an interactive control that allows the user to extend the length of time between each update to as much as ten times the default. The control can be operated with either a mouse or a keyboard.
  • An essential animation can be paused without affecting the activity
    A Website helps users understand ‘how things work’ through animations that demonstrate processes. Animations have “pause” and “restart” buttons.
  • A stock ticker
    A stock ticker has “pause” and “restart” buttons. Pausing the ticker causes it to pause on the currently displayed stock. Restarting causes the ticker to resume from the stopped point but with a notice that the display is delayed. Since the intent of the stock ticker is usually to provide real time information, there might also be a button that would advance the ticker to the most recently traded stock.
  • A test is designed so that time to complete the test does not affect the scoring
    Rather than calibrating an on-line test using a time limit, the test is calibrated based on scores when users have no time limits.
  • A game is designed so that users take turns rather than competing in real-time
    One party can pause the game without invalidating the competitive aspect of it.

• Example 1. Setting user preferences

The preferences page of a Web portal includes an option to postpone all updates and alerts until the end of the current session, except for alerts concerning emergencies.

• A Web site has video of muzzle flash of machine gun fire, but limits the size of the flashing image to a small portion of the screen below the flash threshold size.
• A movie with a scene involving very bright lightning flashes is edited so that the lightning only flashes three times in any one second period.
• Ensuring that content does not violate spatial pattern thresholds.

• Limiting the number of links per page
• Providing mechanisms to navigate to different sections of the content of a Web page 
• Making links visually distinct
• Highlighting search terms

• Setting expectations about content in the page from uncontrolled sources
• Providing sign language interpretation for all content
• Using the clearest and simplest language appropriate for the content
• Avoiding centrally aligned text
• Avoiding text that is fully justified (to both left and right margins) in a way that causes poor spacing between words or characters
• Using left-justified text for languages that are written left to right and right-justified text for languages that are written right-to-left
• Limiting text column width
• Avoiding chunks of italic text
• Avoiding overuse of different styles on individual pages and in sites 
• Making links visually distinct
• Using images, illustrations, video, audio, or symbols to clarify meaning
• Providing practical examples to clarify content
• Using a light pastel background rather than a white background behind black text
• Avoiding the use of unique interface controls unnecessarilyUsing upper and lower case according to the spelling rules of the text language
• Avoiding unusual foreign words
• Providing sign language versions of information, ideas, and processes that must be understood in order to use the content
• Making any reference to a location in a Web page into a link to that location
• Making references to a heading or title include the full text of the title 
• Providing easy-to-read versions of basic information about a set of Web pages, including information about how to contact the Webmaster
• Providing a sign language version of basic information about a set of Web pages, including information about how to contact the Webmaster

Positioning labels to maximize predictability of relationships

Hiding optional form fields

• Avoiding deprecated features of W3C technologies.
• Not displaying content that relies on technologies that are not accessibility-supported when the technology is turned off or not supported.