The accessibility of Information Technology is often summarized in four key principles.  Accessible IT should be Perceivable, Operable, Understandable, and Robust.  These are collectively known as the POUR principles, and are described below.


Perceivable means the user can recognize content and interface elements by means of the senses.  For many users, this means experiencing a system primarily visually. For some users, perceivability may be a matter of sound or touch.


Operable means that a user can successfully use buttons, navigation, and other necessary controls to interact with a website or application.  For many users, this means identifying an interface control visually, and then clicking, tapping, or swiping.  For some users, using a computer keyboard, issuing voice commands, using a motion detector, or some other method may be necessary to operate and control the interface.


Understandable technology is consistent in its presentation and format, predictable in its design and usage patterns, concise, multimodal, and appropriate to the audience in its voice and tone.  Users should be able to comprehend the content, and learn and remember how to use the interface.


Robust I.T. is standards-compliant, and designed to function on all appropriate technologies.  Users should be able to choose the technology they use to interact with websites, online documents, multimedia, and other information formats.