Section 508 is a federal amendment that requires all websites to be accessible by people with disabilities. You can read about Section 508 online. We have provided several tools to help you validate your website and tutorials specifically aimed at Section 508.
Usability means that your website is easy to use, no matter who is trying to use it. Thus, Web designers will pay attention to things like color and placement in order to draw attention, easy-to-understand navigation, scanability, and more. Read more about the difference between accessibility, usability, and Web standards. From web accessibility consultant Jim Thatcher. This site offers an explanation of each Section 508 requirement using very easy-to-understand language and simple, non-complex code examples. This might be a good place to start in order to understand the requirements before delving into some of the more complex tutorial sites.
The site incorporates a number of accessibility aids and contains relevant articles on the subject. The site also gives information about the development of the site and the way the technologies used are supported by different browsers.