On November 3, 2008, the W3C published the Web Content Accessibility Guidelines 2.0. These guidelines include a number of recommendations that developers can use to make content more accessible to people with disabilities and to everyone in general.
Understanding the WCAG Guidelines
WCAG 2.0 is a set of proposed recommendations and as such the W3C Advisory Committee members have until December 2 to send formal review comments to the W3C Team before the recommendations become an official standard.
The 12 proposed guidelines are based on four guiding principles of accessibility:
Accessibility Principle 1 -- Perceivable
"Information and user interface components must be presentable to users in ways they can perceive" Here we find guidelines such as providing alternate text for non-text content (including things like CAPTCHA), alternatives for time-based media, the ability to present content in different formats and to make it easy to see and hear content (separate from things like foreground and background).
Accessibility Principle 2 -- Operable
"User interface components and navigation must be operable" Keyboard accessibility, timing adjustable to give users enough time to read the content, doesn't cause seizures, easy to navigate and not get lost -- these are all guidelines to making a website more operable.
Accessibility Principle 3 -- Understandable
"Information and the operation of user interface must be understandable" To make a website more understandable you need to make it readable, make it consistent in how it looks and works, and provide user input assistance where necessary.
Accessibility Principle 4 -- Robust
"Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies" Robust content means it can be accessed from a wide variety of user agents now and in the future. You do this by ensuring content created using markup languages has been correctly and completely written and that all interface components can have their name, value pairs programatically determined and set.
Accessibility is Not Just About Content
To make a website truly accessibility, then it more than the web content needs to be modified. It's also about Web browsers, other user agents and authoring tools.
These guidelines do not provide the methods in which you achieve them. They have been tested to ensure they are feasible, but how you choose to implement them is dependent on the technology you are using.
In addition to the WCAG 2.0, the Web Accessibility Initiative is also working on Recommendations for Accessibility in Rich Internet Applications.
Get more information on the W3C Accessibility website.