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. 

Examples

• An online assessment contains numerous input fields.  If a user cannot see the field labels, how can she successfully complete the assessment?
• A chart describes the change in a population over time.  If a user cannot see the chart, how can she understand the data?
• An online video narrates a process for completing a task.  If the video is uncaptioned, can a Deaf or Hard of Hearing user learn from the training how to complete the task?
• An article in your LMS is presented as a scanned PDF.  If a user cannot read the PDF, can he learn the content of the article?
• A website's contact information is displayed in the footer. If the background/foreground contrast is insufficient, can a low-vision or color-blind user contact the site owner?

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.

Examples

• A navigation menu reveals a submenu of links when a user hovers over it with a mouse.  If the menu doesn't expand when it receives focus, can a keyboard user access the submenu?
• A website's social media links can be activated with a click of the mouse.  If the links don't receive keyboard focus, can a keyboard user follow the links to social media?
• An online survey permits a user to make multiple selections from a drop-down menu.  If the user cannot simultaneously press a Control key and click on the menu, can she make multiple selections?

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.

Examples

• A website's navigation consists of a number of links that are displayed in a different order and location from page to page.  If a user has to relearn basic navigation for each page, can she effectively move through the website?
• A registration form contains required email and phone number fields.  If the form doesn't inform the user when there is an input error, can the user understand why the form cannot be submitted?
• A document contains a number of non-English words and phrases. If the languages are not indicated, can assistive technology present the text correctly?

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.

Examples

• A website requires a specific version of a web browser to make use of its features.  If a user doesn't or can't use that browser, can that user experience the features of the site?
• A document format is inaccessible to a screen reader on a particular operating system.  If a user employs that OS for day-to-day tasks, can she gain access to the document?
• An online educational resource requires an inaccessible plug-in to work in the web browser.  If the user can't use the plug-in, can he meet the educational objective?