Accessibility standards vary at the national, state, local, and institutional levels. Before developing a website, it's important to identify and understand the applicable policy and its implications for your design. Most policies around the world are based on the Web Content Accessibility Guidelines of the W3C. In the United States, these guidelines are the basis of the standards mandated under Section 508 of the Federal Rehabilitation Act. Section 508 standards affect all federal government websites.
Section 508 of the Federal Rehabilitation Act also affects websites developed or maintained by the U.S. government. University websites are not required to conform to Section 508 standards, although some universities may adopt these standards as the basis of an institutional policy. Outside of the United States, the W3C guidelines serve as the basis of most accessibility policies. Australia, Canada, Japan, and the European Union all have accessibility policies based on the W3C guidelines.
Since the introduction of Dreamweaver CS6, Dreamweaver no longer includes a built-in accessibility validation tool. However, there are a number of third party web accessibility evaluation tools. The W3C Web Accessibility initiative provides a comprehensive list of these tools at http://www.w3.org/WAI/RC/tools/