6.2. Accessibility in Web Technologies
Accessibility -- addressing both the needs of the disabled and the
growing usage of alternative and mobile browsing devices by the
general public -- has been a guiding force in the evolution of the
technologies we use to create web content. Under the supervision of
the WAI, both the HTML 4.0 and CSS2 specifications feature many
methods for increasing access to web sites.
6.2.1. HTML 4.01 Features
The HTML 4.01 specification
incorporates a number of new attributes and tags aimed specifically
at making web documents available to a broader audience. This section
lists only a broad summary of accessibility features in HTML 4.01.
For a more detailed listing, see the WAI's HTML
Techniques for Web Content Accessibility Guidelines 1.0
at http://www.w3.org/TR/WCAG10-HTML-TECHS/. Or
tackle the HTML 4.0 Specification yourself at http://www.w3.org/TR/REC-html40/.
Accessibility features of the Specification include:
Increased distinction between document structure and presentation.
HTML 4.0 encourages the use of Cascading Style Sheets for stylistic
Navigational aids such as access keys and tab index for keyboard-only
access to page elements.
A new client-side imagemap recommendation that integrates image and
Introduction of the
and <acronym> tags, which assist speech
devices and other agents in the interpretation of abbreviations and
The ability to group
table columns and rows logically and to
provide captions, summaries, and long descriptions of table contents,
thus making the table interpretation easier.
The ability to group form controls and make long lists of choices
easier to comprehend. Form elements are also accessible via tabbing
and access keys.
Improved mechanisms for providing alternative text. The
alt attribute is now required in the
<img> tag. The
attribute has been introduced to provide
a link to longer text explanations of images. The
title attribute can be added to provide
additional information to any element.
6.2.2. CSS2 Features
The latest Cascading Style Sheets recommendation,
CSS Level 2 (or CSS2), also provides mechanisms for improved
interpretation by nongraphical and nonvisual devices. The following
is just a summary of features. For more information, read the
WAI's review at http://www.w3.org/TR/WCAG10-CSS-TECHS/ or
look at the CSS2 Recommendation directly at http://www.w3.org/TR/REC-CSS2/. Improvements
Mechanisms by which a user-created style sheet can override all the
higher style sheets in the cascade, giving the end user ultimate
control over display. The user can create a custom style sheet for
displaying pages according to special needs.
mechanisms that further separate content from presentation. These
style sheet rules aim to eliminate the abuse of HTML tags in order to
achieve special presentation effects. The HTML tags can be used for
the logical structuring of the document, making them more easily
interpreted by nonvisual agents.
The ability to customize style sheets for a variety of media
(including screen, Braille, aural, etc.) using the
media attribute and @media
rule. Unfortunately, alternative media are not well supported as of
this writing, with the exception of targeting printed output (see
Chapter 5, "Printing from the Web").
A set of controls for the audio rendering of web-delivered
Improved navigation devices, such as the ability to add numbered
markers throughout a document for orientation purposes.
Specific support for downloadable fonts, eliminating the tendency to
put text in graphics to improve the appearance of the page.
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