Section 508
Section 508 is an amendment to an Act that is law in the United States of America. This has been widely accepted as a guideline to accessible website design throughout the world.
History of section 508.
Section 508 was added as an amendment to the Rehabilitation Act of 1973. The original section 508 covered electronic and information technologies, in recognition of the growth of this field.
In 1997 The Federal Electronic and Information Technology Accessibility and Compliance Act was proposed in the US legislature. This was to correct the shortcomings of the original section 508, which was mostly ineffective. This was partly due to the lack of enforcement of the act. The FEITACA, with revisions, was finally enacted as the new Section 508 of the Rehabilitation Act of 1973, in 1998.
There is nothing in section 508 that requires private websites to comply unless they are receiving federal funds or under contract with a federal agency. Best practices include voluntary standards and guidelines such as the W3C and WAI guidelines.
Section 508 tests are one of the tests I carry out as part of the accessibility test on your website. Section 508 compliance tests can also be run separately to check your website complies with these guidelines.