3. The usage of script elements or applets

It must ensure that pages are usable when scripts, applets, or other programmatic objects are turned off or not supported.
If you use a JavaScript for the navigation menu of the page it must be sure that navigation is also possible without the menu.

JavaScript deactivated

Javascript activated

HTML Sourcecode which replace the javascriptmenu:
< noscript >
< a href = " ../../../index.htm " target = " _self " >Home</ a >
< a href = " ../overview.htm " target = " _self " >Courses</ a >

On the left side, you can see the JavaScript menu of the page. On the right side JavaScript is deactivated, the main menu is available in standard HTML Internetlinks. A click on one link forward you to a page which shows the menu items.

This example should give a small impression which problems blind or generally physically handicapped people got with unstructured information on websites.
A Checklist for website development is offered by the W3 - Consortium on the page:
http://www.w3.org/TR/WAI-WEBCONTENT/full-checklist.html

[Example 1: Description of Pictures] [Example 2: Information indicated by color]
[Example 3: Usage of Scripts]