The guidelines also suggest ways of making sites accessible to people using browsers or computers that cannot display certain site features such as images or video, a problem on the rise with the increasing popularity of small computers.
"I'm very excited that we have made this much progress on the page authoring accessibility guidelines," said W3C International Program office director Judy Brewer. "Having a comprehensive and up-to-date resource on Web accessibility will be very useful for people doing Web design and development. Certainly public organizations need to be accessible to their entire public, and private corporations don't want to miss out on any part of their market."
Many of the guidelines released today are specific to the new capabilities of HTML 4.0, which the W3C's Web Accessibility Initiative (WAI) helped design and in December formally recommended. HTML 4.0, for example, provides support for screen readers, which translate text to speech synthesis or refreshable Braille displays. It also provides support for audio browsers, which provide speech synthesis, and text-only browsers, which can't display images.
HTML 4.0 requires the use of "alt text," or alternative text, which sits "behind" images and describes them. HTML 4.0 allows more thorough alt text descriptions. It also offers ways of organizing and identifying information in forms and tables, and improves support for keyboard navigation.
One important ingredient in both HTML 4.0 and the guideline draft released today is support for cascading style sheets, which carry the design information for a page and work either from the server or the client end. A client-side style sheet, for example, would let a visually impaired Web surfer specify background and text colors that are easiest for him or her to read.
The guidelines fall into three categories, suggesting accessibility improvements in document structure, navigation, and alternative formatting of content. The guidelines also provide an accessibility checklist and suggestions for evaluating sites.
The WAI's proposed guidelines, which drew on a similar set published by various organizations and corporations, must go through a period of public comment before becoming an official recommendation.
The WAI currently is working on two other accessibility initiatives, one for use in creating browsers, the other for designing authoring tools.