2.27 Avoid deprecated features of W3C technologies
WAI checkpoint 11.2
Full WAI text: "Avoid deprecated features of W3C technologies." A "deprecated" feature is one which the W3C wants to remove from the official standard for a given technology but which has not yet become officially obsolete or removed. Even though they are part of the official standard, the W3C discourages the use of deprecated features. For example, the "font" tag in HTML is an example of a deprecated feature in HTML 4.0.
The World Wide Web Consortium (W3C) is an independent, international body that creates Internet and programming language standards. Its recommendations and standards are highly regarded.
W3C technologies are continually reviewed for accessibility so that the latest versions may have discarded some features which have been found to hinder accessibility. By using a current W3C technology, you are more likely to embed accessibility in your website.
Directions and Techniques
Consult the W3C list of HTML elements and attributes
The index of HTML elements and attributes lists all elements in HTML 4.0. Deprecated elements are indicated with an asterisk.
Write Cascading Style Sheets (CSS) which support user override of styles
Users can override CSS with their own style sheets, which may be configured to suit their needs. This is an important feature of CSS and should be provided. See the WAI recommended techniques for user override of styles.
Avoid using deprecated features for presenting fonts
See the WAI recommended techniques for specifying font styles.
How you could check for this:
Test with the W3C HTML validator
The W3C HTML validator can check HTML to ensure that it validates to formal grammars. The W3C also provide a comprehensive list of the formal grammars which it uses. Some authoring tools also include validators. If you use an authoring tool, you should ensure that the validator is up to date and validates for deprecated features.