There are a number of legal requirements and standards for accessibility on the Web. The most important of these is the Americans with Disabilities Act (ADA), which prohibits discrimination against people with disabilities in all areas of public life, including the Internet.
Other important legal requirements and standards for accessibility on the Web include the World Wide Web Consortium's (W3C) Web Content Accessibility Guidelines (WCAG), which provide detailed guidance on how to make web content more accessible to people with disabilities; and the Section 508 Standards, which require that all electronic and information technology procured by the US federal government be accessible to people with disabilities.
Making your website accessible to people with disabilities is not only the right thing to do, it is also good for business. People with disabilities represent a large and growing market, and making your website accessible to them will give you a competitive edge.