Basically, online content and services can be deemed ‘Section 508 Compliant’ if they meet standards laid out by the Federal Government in Section 508 (or the Electronic and Information Technology Accessibility Standards, 36 C.F.R. § 1194 added to the act in 1998) of the Rehabilitation Act of 1973 (or 29 U.S.C.A. § 794d).
The amendment 508 is designed to standardize the accessibility of information technology not just the Web. It requires all US federal agencies to make their products accessible for all users regardless of abilities. Also, these agencies must purchase goods and services that meet the 508 standard.
508 has equivalents in WCAG 1.0 or Web Content Accessibility Guidelines 1.0. Rather than being law, they are guidelines set forth by W3C to promote accessibility for all users. Examples of increased accessibility features include use of text alternatives, fonts with increased readability, closed captioning in video posts, scripting workarounds to accommodate some assistive technologies and color alternatives.