There is a legal requirement for UK websites to provide web pages that are accessible to disabled users. All important website content should comply to at least Priority Level A as laid down by the World Wide Web Consortium Accessibility Guidelines.
As well as the legal and moral argument for accessibility, it makes no sense to exclude such a large group of users. A fully accessible website presents a more professional and responsible image and is more likely to be linked to from quality sites and search engines.
Accessibility Ratings
The W3C have set 3 levels of accessibility, A, AA and AAA, and provide Web Content Accessibility Guidelines that set Priorities that documents either...
Must satisfy - Priority 1
Should satisfy - Priority 2
May satisfy - Priority 3
To meet accessibility level A then the document must satisfy all Priority 1 checkpoints but need not satisfy all the Priority 2 and 3 checkpoints.
To meet accessibility level AA then the document must satisfy all Priority 1 and Priority 2 checkpoints but need not satisfy all 3 checkpoints.
To meet accessibility level AAA then the document must satisfy all Priority 1, 2 and 3 checkpoints.
Accessibility Audit and Validation
To properly check if a web page meets accessibility standards requires an audit that meets the W3C Accessibility Guidelines. Validators are available and useful but there is a limit to how much they can do since many of the checkpoints require manual checking.
Until recently the WebXact validator was available online, but has now been withdrawn. However, developers can still validate using the Wave Validator.
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