There are four key principles that guide the WCAG guidelines: Perceivable - users must be able to perceive the information being presented (it cannot be invisible to all of their senses). The specific WCAG guidelines around this principle are: - Provide text alternatives for non-text content. - Provide captions and other alternatives for multimedia. - Create content that can be presented in different ways, including by assistive technologies, without losing meaning. - Make it easier for users to see and hear content. Operable - users must be able to operate the interface (the interface cannot require interaction that a user cannot perform). The specific WCAG guidelines around this principle are: - Make all functionality available from a keyboard. - Give users enough time to read and use content. - Do not use content that causes seizures or physical reactions. - Help users navigate and find content. - Make it easier to use inputs other than the keyboard. Understandable -  users must be able to understand the information as well as the operation of the user interface (the content or operation cannot be beyond their understanding). The specific WCAG guidelines around this principle are: - Make text readable and understandable. - Make content appear and operate in predictable ways. - Help users avoid and correct mistakes. Robust - users must be able to access the content as technologies advance (as technologies and user agents evolve, the content should remain accessible). The specific WCAG guidelines around this principle are: - Maximize compatibility with current and future user tools.