Web Content Accessibility Guidelines - Overview

Original Author(s): Markus Gylling
Note that a new version - Web Content Accessibility Guidelines (WCAG) 2.0 has been released since this article was written. Visit the WCAG 2.0 Introduction page on the W3C website for details on the newer version.

Web Content Accessibility Guidelines 1.0

W3C Recommendation 5-May-1999
  • explain how to make web content accessible to people with disabilities
  • intended for
    • web content developers (page authors and site designers)
    • developers of authoring tools
  • primary goal: to promote accessibility
  • make web content more available to all users,
    • irrespective of user agent
      (desktop browser, voice browser, mobile phone, automobile-based personal computer, etc.)
    • irrespective of operating constraints
      (noisy surroundings, under- or over-illuminated rooms, in a hands-free environment, etc.)
  • do not discourage content developers from using images, video, etc.,
    but rather explain how to make multimedia content more accessible to a wide audience

Fourteen Guidelines, with elaborate practical checkpoints for each

Accompanied with separate Techniques documents that further exemplify implementation of the guidelines

  1. Provide content that, when presented to the user, conveys essentially the same function or purpose as auditory or visual content.
    • Provide text equivalents of non-text content (images, pre-recorded audio, video).
    • The power of text equivalents lies in their capacity to be rendered in ways that are accessible to people from various disability groups using a variety of technologies.
    • Providing non-text equivalents (e.g., pictures, videos, and pre-recorded audio) of text is also beneficial to some users, especially nonreaders or people who have difficulty reading.
  2. Ensure that text and graphics are understandable when viewed without color.
    • If color alone is used to convey information, people who cannot differentiate between certain colors and users with devices that have non-color or non-visual displays will not receive the information.
  3. Mark up documents with the proper structural elements. Control presentation with style sheets rather than with presentation elements and attributes.
    • Use, not misuse, structural markup to convey information
    • Use Stylesheet for presentational layer
    • Fosters accessibility and device independence
  4. Use markup that facilitates pronunciation or interpretation of abbreviated or foreign text.
    • In addition to helping assistive technologies (such as screenreaders), natural language markup allows search engines to find key words and identify documents in a desired language. Natural language markup also improves readability of the Web for all people, including those with learning disabilities, cognitive disabilities, or people who are deaf.
  5. Ensure that tables have necessary markup to be transformed by accessible browsers and other user agents.
    • Tables should be used to mark up truly tabular information ("data tables").
    • Content developers should avoid using them to lay out pages ("layout tables").
    • Tables for any use also present special problems to users of screen readers
    • Some user agents allow users to navigate among table cells and access header and other table cell information. Unless marked-up properly, these tables will not provide user agents with the appropriate information.
  6. Ensure that pages are accessible even when newer technologies are not supported or are turned off.
    • Although content developers are encouraged to use new technologies that solve problems raised by existing technologies, they should know how to make their pages still work with older browsers and people who choose to turn off features.
  7. Ensure that moving, blinking, scrolling, or auto-updating objects or pages may be paused or stopped.
    • Some people with cognitive or visual disabilities are unable to read moving text quickly enough or at all.
    • Movement can also cause such a distraction that the rest of the page becomes unreadable for people with cognitive disabilities.
    • Screen readers are unable to read moving text.
    • People with physical disabilities might not be able to move quickly or accurately enough to interact with moving objects.
  8. Ensure that the user interface follows principles of accessible design: device-independent access to functionality, keyboard operability, self-voicing, etc.
    • When an embedded object has its "own interface", the interface -- like the interface to the browser itself -- must be accessible.
  9. Use features that enable activation of page elements via a variety of input devices.
    • Device-independent access means that the user may interact with the user agent or document with a preferred input (or output) device -- mouse, keyboard, voice, head wand, or other.
  10. Use interim accessibility solutions so that assistive technologies and older browsers will operate correctly.
    • For example, older browsers do not allow users to navigate to empty edit boxes. Older screen readers read lists of consecutive links as one link. These active elements are therefore difficult or impossible to access. Also, changing the current window or popping up new windows can be very disorienting to users who cannot see that this has happened.
    • (... apply until user agents (including assistive technologies) address these issues)
  11. Use W3C technologies (according to specification) and follow accessibility guidelines. Where it is not possible to use a W3C technology, or doing so results in material that does not transform gracefully, provide an alternative version of the content that is accessible.
    • W3C technologies include "built-in" accessibility features.
    • W3C specifications undergo early review to ensure that accessibility issues are considered during the design phase.
    • W3C specifications are developed in an open, industry consensus process.
  12. Provide context and orientation information to help users understand complex pages or elements.
    • Grouping elements and providing contextual information about the relationships between elements can be useful for all users.
    • Complex relationships between parts of a page may be difficult for people with cognitive disabilities and people with visual disabilities to interpret.
  13. Provide clear and consistent navigation mechanisms -- orientation information, navigation bars, a site map, etc. -- to increase the likelihood that a person will find what they are looking for at a site.
    • Clear and consistent navigation mechanisms are important to people with cognitive disabilities or blindness, and benefit all users.
  14. Ensure that documents are clear and simple so they may be more easily understood.
    • Consistent page layout, recognizable graphics, and easy to understand language benefit all users. In particular, they help people with cognitive disabilities or who have difficulty reading.
    • Validate accessibility with automatic tools and human review.
    • Automated methods are generally rapid and convenient but cannot identify all accessibility issues.
    • Human review can help ensure clarity of language and ease of navigation.

Read More

DAISYpedia Categories: 


This page was last edited by PVerma on Saturday, August 28, 2010 20:43
Text is available under the terms of the DAISY Consortium Intellectual Property Policy, Licensing, and Working Group Process.