Accessibility with Section 508 and WCAG
Websites should be accessible to people with disabilities. The section 508 standards specification shows what must be considered to do so. Part of it is the paragraph 1194.22, dedicated to web-based intranet and internet information and applications. As a designer you must also consider WCAG 2.0 (Web Content Accessibility Guidelines) and the guide to understanding and implementing WCAG 2.0. The latter discusses text alternatives, time-based media, adaptability, distinguishability, keyboard accessibility, time constraints, seizures, navigability, readability, predictability, input assistance and compatibility and more.
Inaccessible information is a barrier to the two-way communication between users and sites. I would like to recommend the documents above as a way to enhance the user experience.