2.4.2 Meeting the guidelines for the fourth principle, robust

The following are some of the points that you might want to keep in mind when creating web content and web sites that meet the Web Content Accessibility Guidelines 2.0 principle of robust.

Robustness is generally achieved by ensuring your web pages adhere to accepted standards, and by ensuring compatibility with browsers and other applications and technologies like assistive software and hardware. There is only one guideline with just two success criteria for this principle, and both must be met to achieve Level A.

  • When you employ established web technologies to create accessible websites, make sure that you use them according to their published standards.
    • For example, XHTML Strict has clear rules about matching an element's start and end tags. If you indicate in your code that you are following the language of XHTML Strict and you do not do so then the web browsers and the assistive devices, which are expecting valid or correct code might not work or if they do, work inconsistently. Most have automated validation or debugging tools you will want to use to ensure that the pages are free of errors.
  • When you use proprietary extensions of an established web technology make sure that it is compatible with the browsers that users employ.
    • The developers of browsers occasionally seek to distinguish their products from others on the market by supporting elements or attributes that are not part of the standard of the base mark-up language. These extensions do something when they encounter browsers that understand them. The extensions, however, might not work in other browsers. Consequently, any content or functionality specified by these extensions may be inaccessible to a large number of users.
  • When you employ features of established web technologies that are deprecated, some assistive technologies might not work with them.
    • To be deprecated means the feature is being phased out over time in a technology's core set of features. For example, HTML elements such as <center>, <font>. <u> were deprecated when HTML4 was introduced. Many web pages still used these and other deprecated elements because most browsers still recognize them. But as the standards change, support for deprecated items might disappear from standard conforming technologies and especially from assistive technologies that assume wide implementation.

Visit the following links to access more specific information on coding techniques related to the creation of robust Web content including comparability with current and future tools: