See more recent information:
Accessibility is the ability to use the Internet even when functioning under constraints. Examples of constraints that impact web use include:
Accessibility is not only about disability. It is about addressing the range of constraints that could limit your customers' ability to use your site.
Accessibility is about making web sites "transform gracefully" so that they serve more people, in more situations. Providing an accessible web site means:
Historically, "accessibility" meant designing for people with functional limitations, or disabilities. Over time, the relationships between designing for functional limitations, designing for experienced users without limitations, and designing for situational limitations became apparent. The result was the development of "universal design" - a method for creating products (in this case, web sites) that are usable by people with the widest range of abilities, operating within the widest range of situations.
Recent regulatory and legal activities are providing powerful impetus for organizations to make web sites accessible. Section 508 of the Rehabilitation Act applies to electronic and information technology of the Federal government. The Americans with Disabilities Act (ADA) is successfully being applied to web sites of organizations and businesses.
One market that benefits from universal design is older customers and customers with disabilities. Between 15% and 30% of the population has functional limitations that can affect their ability to use web sites and other products, and this number is increasing as the population ages. Furthermore, the stereotype of the youthful Internet generation does not fit the reality of the online buyer. As Computerworld reported:
Many people with disabilities and older people have additional motivations for shopping online instead of at "bricks and mortar" stores. These include limited transportation, limited energy or ability to walk, and difficulty carrying packages.
Another market segment that benefits from accessible web pages is those accessing the Internet in constraining environments, conditions, and circumstances. This includes the executive buying a gift from a hand-held device, or checking flight status from a web-enabled mobile phone. Personal digital assistants (PDAs), wireless telephones, and other devices are increasingly able to access the web. These devices have limited input and output options, such as small displays, which are optimized by following accessibility guidelines. It bears noting that these devices tend to be purchased by high-end buyers.
The result of considering accessibility and practicing universal design is simply that more people can use your web site in more situations.