Web Content Accessibility Guidelines (WCAG) 2.0 is a standards document from the World Wide Web Consortium (W3C). Here’s a summary of what the guidelines are and a brief hint as to what the guidelines involve.
Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language. This will include sign language video for audio only files.
All non-text content that is presented to the user has a text alternative that serves the equivalent purpose. There are certain exceptions to this, including form input controls, alternatives for CAPTCHA, and making purely decorative images invisible to assistive technology. This recommendation is complex and there are a number of techniques suggested that may or may not be helpful in meeting it, for example, using label elements to associate text labels with form controls and using the title attribute to identify form controls when the label element cannot be used.
Provide alternatives for time-based media. This involves audio or video synchronized with another format for presenting information and/or with time-based interactive components. For example, an audio instruction to “click now” might need to be augmented with synchronized captions.
Create content that can be presented in different ways (for example simpler layout ) without losing information or structure. This includes the way the parts of a Web page are organized in relation to each other; and the way a collection of Web pages is organized. It also means that rendering the content in a form that can be perceived by all users is possible.
Make it easier for users to see and hear content including separating foreground from background. This includes the choice of fonts, color, highlighting, audio controls, and contrast.
Except for captions and images of text, text can be resized without assistive technology up to 200 percent without loss of content or functionality. This includes using relative measures (such as ems) for both text size and container size.
Make all functionality available from a keyboard. This doesn’t exclude the use of a mouse, just the that functionality must be available without a mouse.
Provide users enough time to read and use content. There must be a way to turn things off or adjust the timing.
Do not design content in a way that is known to cause seizures. There are techniques explaining what is called the “three flashes or below threshold” for flashing content.
Provide ways to help users navigate, find content and determine where they are. This includes ways to bypass blocks of content with skip links and/or heading elements, page titles, visible focus, and clear textual cues to link purpose.
Make text content readable and understandable. This involves language choices, abbreviations, reading level and pronunciation.
Make Web pages appear and operate in predictable ways. Things must operate in expected ways, be consistent, and the use identification of elements with symbols such as arrows must be consistent and clear.
Help users avoid and correct mistakes. Errors must be described and explained, instructions and help must be provided when needed.
Maximize compatibility with current and future user agents, including assistive technologies. That means use valid markup and follow the standards.
There are various levels of conformance for the WCAG 2.0 guidelines. The use of some techniques may be consider sufficient, even though there may be techniques that go beyond the level of “sufficiency.”