Accessibility
Web accessibility refers to the practice of making websites usable by people of all abilities and disabilities. When sites are correctly designed, developed and edited, all users can have equal access to information and functionality.
The W3C's Web Accessibility Initiative (WAI) Introduction to Web Accessibility says Web accessibility means that people with disabilities can use the Web. More specifically, Web accessibility means that people with disabilities can perceive, understand, navigate, and interact with the Web, and that they can contribute to the Web. Web accessibility also benefits others, including older people with changing abilities due to aging
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This is a guide on accessibility best practice for theme developers. The Drupal theme layer is extremely powerful and you can incorporate many accessibility features via the sites theme—the flip side is that you can also make many mistakes. This guide intends to provide a roadmap towards better accessibility for all Drupal themes.
The intended audience is anyone who is building a theme for Drupal, having a theme built or wants to improve their existing theme.
The guide is not exhaustive, however where appropriate links to external resources are provided for further reading.

Seemed redundant at first....
But the rationale outlined at http://groups.drupal.org/node/22226#comment-77178 makes sense.
John, there's an issue open
John, there's an issue open in the docs queue - http://drupal.org/node/462532, which is a better place to discuss. Regarding your point, some of it is very Drupal specific stuff and will no doubt be redrafted to be more so. I am also writing tutorials to go here which of course are very Drupal specific.
The decision to include generalised information stems from the fact (and I do believe this is a fact) that for many this may be the only accessibility documentation they ever read. Granted, there is a great body of work available, however its a lot of work to piece it all together. I have personally spent hundreds of hours reading online documentation and finding ways of improving accessibility in Drupal themes. I would think that most people will not do that. I believe most themers need a primer and some how to's; that's what this documentation aims to achieve.
There are links and references to some fantastic resources, tools and soon some simple tutorials will be added. I personally think this is great resource.
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