Web Content Accessibility Guidelines
Web Content Accessibility Guidelines (WCAG) are part of a series of Web accessibility guidelines published by the W3C's Web Accessibility Initiative. They consist of a set of guidelines for making content accessible, primarily for disabled users, but also for all user agents, including highly limited devices, such as mobile phones. The current version, 2.0, is also an ISO standard, ISO/IEC 40500:2012.
WCAG 1.0 
The WCAG 1.0 was published and became a W3C recommendation on 5 May 1999. They have since been superseded by WCAG 2.0.
WCAG 1.0 has three priority levels:
- Priority 1: Web developers must satisfy these requirements, otherwise it will be impossible for one or more groups to access the Web content. Conformance to this level is described as A.
- Priority 2: Web developers should satisfy these requirements, otherwise some groups will find it difficult to access the Web content. Conformance to this level is described as AA or Double-A.
- Priority 3: Web developers may satisfy these requirements, in order to make it easier for some groups to access the Web content. Conformance to this level is described as AAA or Triple-A.
WCAG Samurai 
In February 2008, The WCAG Samurai, a group of developers independent of the W3C, and led by Joe Clark, published corrections for, and extensions to, the WCAG 1.0.
WCAG 2.0 
WCAG 2.0 was published as a W3C Recommendation on 11 December 2008. The lengthy consultation process prior to this encouraged participation in editing (and responding to the hundreds of comments) by the Working Group, with diversity assured by inclusion of accessibility experts and members of the disability community.
The Web Accessibility Initiative is also working on guidance for migrating from WCAG 1.0 to WCAG 2.0. A comparison of WCAG 1.0 checkpoints and WCAG 2.0 success criteria is already available.
WCAG 2.0 uses the same three levels of conformance as WCAG 1.0, but has redefined them. The WCAG working group maintains an extensive list of web accessibility techniques and common failure cases for WCAG 2.0.
Earlier guidelines 
The first web accessibility guideline was compiled by Gregg Vanderheiden and released in January 1995 just after the 1994 WWW II in Chicago (where Tim Berners-Lee first mentioned disability access in a keynote speech after seeing a pre-conference workshop on accessibility led by Mike Paciello).
Over 38 different Web access guidelines followed from various authors and organizations over the next few years. These were brought together in the Unified Web Site Accessibility Guidelines compiled by the at the University of Wisconsin-Madison. Version 8 of the Unified Web Site Accessibility Guidelines, published in 1998, was used as the starting point for the W3C's WCAG 1.0.
Legal obligations 
Businesses that have an online presence should provide accessibility to disabled users. Not only are there ethical and commercial justifications for implementing the Web Content Accessibility Guidelines, there are also legal reasons. If a business's website does not meet the Accessibility Guidelines, then the website owner could be sued for discrimination.
To date, at least two actions against websites have been initiated by the Royal National Institute for the Blind (RNIB) in the United Kingdom, and both settled without the case being heard by a court. The RNIB opted not to name the two companies that faced settlements.
Additionally, there has been one case of electronic accessibility that resulted in an employment tribunal finding discrimination. The case, against the Project Management Institute (PMI), was decided in October 2006, and the company was ordered to pay compensation of £3,000.
The landmark 2010/2012 Jodhan decision has caused the Canadian Federal government to require all online web pages, documents and videos available externally and internally to meet the accessibility requirements of WCAG 2.0.
The Australian Government has also mandated that all Australian Government websites meet the WCAG accessibility requirements.
It is anticipated that higher-profile test cases will be launched against non-compliant websites in the near future. Since the law requires websites to take "reasonable steps" to make websites accessible to users, it is anticipated that large companies will struggle to justify any failures to make their websites accessible, while small businesses and charities may have a better defense, if they can show that they do not have the resources necessary for the development work.
- Web Content Accessibility Guidelines (WCAG) 2.0 – W3C Recommendation 11 December 2008
- W3C: W3C Web Standard Defines Accessibility for Next Generation Web (press release, 11 December 2008).
- Comparison of WCAG 1.0 Checkpoints to WCAG 2.0, in Numerical Order
- Techniques for WCAG 2.0
- Henry, Shawn (2012-10-15). "WCAG 2.0 is now also ISO/IEC 40500!". World Wide Web Consortium. Retrieved 23 October 2012.
- "W3C Web Content Accessibility Guidelines 2.0 approved as an ISO/IEC International Standard". World Wide Web Consortium. 2012-10-15. Retrieved 23 October 2012.
- "ISO/IEC 40500:2012 - Information technology -- W3C Web Content Accessibility Guidelines (WCAG) 2.0". ISO. Retrieved 23 October 2012.
- Vanderheiden, Gregg C. (31 January 1995). "Design of HTML (Mosaic) Pages to Increase their Accessibility to Users with Disabilities; Strategies for Today and Tomorrow". Trace Center, University of Wisconsin–Madison. Retrieved 2012-09-22.
- "References: Designing Accessible HTML Pages -- guidelines and overview documents". World Wide Web Consortium. Retrieved 2012-09-22.
- "Trace Center". Trace Center, University of Wisconsin–Madison. Retrieved 2012-09-22.
- Vanderheiden, Gregg C.; Chisholm, Wendy A., eds. (20 January 1998). "Unified Web Site Accessibility Guidelines". Trace Center, University of Wisconsin–Madison. Retrieved 2012-09-22.
- Commercial Justifications for WCAG 2.0
- Computer-based exam discriminated against blind candidate
- Jodhan decision
- Canadian Treasury Board Secretariat Standard on Web Accessibility
- WCAG 1.0
- WCAG 2.0
- WAI Introduction to WCAG
- WAVE – Online Accessibility validator
- Achieving WCAG 2.0 with PDF/UA