1. Pictures which contains information must be described by text

Every picture, which contains valuable information must be described by a special HTML attribute of the element " img" . This attribute is called " longdesc " and is not viewable by standard web browser like Internet Explorer. Screen reader programs for blind people use the information in the longdesc attribute to give the user information about the picture.

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] [WAI Startpage]