Signed in 1990 at a time that most people hadn’t even used the Internet, the Americans with Disabilities Act does not explicitly regulate how websites need to follow nondiscrimination requirements. We now know that using the Internet is one of the most important ways for people with disabilities to fulfill their needs and desires. For many people with disabilities, especially impairments to sight and motion, visiting a store or other physical location can be a challenging experience. Online shopping, for example, allows people with disabilities to make the purchases they need easily and securely within the comfort of their own homes.
Level AA is a little more significant, and makes sites accessible to people with a wider range of disabilities, including the most common barriers to use. It won't impact the look and feel of the site as much as Level AAA compliance, though it does include guidance on color contrast and error identification. Most businesses should be aiming for Level AA conformity, and it appears to reflect the level of accessibility the DOJ expects.