Baseline (in WCAG 2.0) is a set of technologies that a user agent (browser, media player, screen reader etc.) is assumed to support and have enabled. It may be set by the author or higher authority. When an author makes a WCAG 2.0 conformance claim, they must specify the baseline that they are using to make that claim. The author is claiming that their content will meet WCAG 2.0 at the stated level of conformance if a userâ€™s agent can support those (the baseline) technologies.. It's important to note that the baseline consists of technologies that are assumed to be supported by user-agents, and not specific user agents. The concept of baseline is based around trust. It is very possible to abuse baselines by declaring technologies that are not widely supported and not widely supported by assistive technology. For more information visit About Baselines and WCAG 2.0.
a set of technologies set by the author (or more likely their company, or maybe a higher level like a government) that are assumed to be available in the client, such as HTML , CSS , scripting, GIF , jpg, MPEG , etc
Set of technologies assumed to be supported by, and enabled in, user agents in order for Web content to conform to these guidelines. Note: Some examples of entities that may set baselines that an author may have to follow include the author, a company, a customer and government entities.