Quick Reference
Web Accessibility Principles

Principles of Accessibility

• Perceivable - Available through sight, hearing, or touch.
• Operable - Compatible with keyboard or mouse.
• Understandable - User-friendly, easy to comprehend.
• Robust - Works across browsers, assistive technologies, mobile devices, old devices/browsers, etc. Follows standards.

webaim.org/articles/pour/

Provide appropriate alternative text

• Every non-text element needs a text alternative (alt text) that provides an equivalent to the image content.
• Alt text should present the content and function, not necessarily a description, of an image.
• If an image has no relevant content or function, is decorative, or the alternative text is provided in nearby text, then the image should have an empty alternative text value (alt="").
• If an image is a link (or hotspot), the alt text must describe the link’s function.
• Avoid words like "picture of," "image of," or "link to."
• Use the fewest number of words necessary.

webaim.org/techniques/alttext/

Content is well structured and clearly written

• Use the simplest language appropriate for your content.
• Organize your content using true headings (e.g., <h1>) and lists.
• Use empty (white) space to improve readability.
• Use illustrations, icons, etc. to supplement text.
• Check spelling, grammar, and readability.

Help users navigate to relevant content

• Provide a link that allows the user to skip over navigation to the main content in the page.
• Use true headings to organize content.

Provide headers for data tables

• Identify all data table headers using the <th> element.
• Provide an appropriate scope attribute: <th scope="col"> for column headers or <th scope="row"> for row headers.
• If appropriate, add a table <caption> for the data table.

webaim.org/techniques/tables/

Do not rely on color alone to convey meaning

• The use of color can enhance comprehension, but do not use color alone to convey information. Be especially cautious of red/green color combinations.
• Make sure that color contrast is strong, especially between text and background.

webaim.org/articles/visual/colorblind/

Ensure users can complete and submit all forms

• Put form labels adjacent to or near their controls, so the labels are associated visually.
• Use the <label> element to associate labels and controls.
• Group similar elements (such as checkboxes or radio buttons) together using <fieldset>.
• Clearly identify required form elements. Don't make a field required if it is not necessary. Ensure all directions and cues are readily accessible.
• If there are errors in a form that has been submitted, alert the user in an accessible way (especially to a screen reader user) and make it easy to fix the incorrect information and resubmit the form.

webaim.org/techniques/forms/

Ensure links make sense out of context

• Avoid phrases like "Click here", "Here", "More", "More information", "Read more", and "Continue."
• URL's as link text should usually be avoided, unless the URL is relevant content.

Caption and/or provide transcripts for media

• Videos and live audio must have captions and a transcript. A transcript is sufficient for archived audio.
• Captions should be synchronized, equivalent, and accessible.

webaim.org/techniques/captions/

Ensure accessibility of non-HTML content

• HTML content will almost always be more accessible than content in any other format.
• PDF, Microsoft Word and PowerPoint files, OpenOffice.org, and Adobe Flash provide basic accessibility features.
• Provide accessible alternatives when non-HTML content cannot be made fully accessible.
• Test the accessibility of non-HTML content in assistive technologies.

Miscellaneous

• Ensure that the page is readable and usable when fonts are enlarged 150-200%.
• Provide a descriptive page <title>.
• When using scripting, ensure events are available with both mouse and keyboard. Make all scripted content and page updates/changes available to screen readers.
• Limit pop-up windows and notify users when pop-ups are used.
• Provide a descriptive title for all frames (e.g., <frame title="navigation">).
• Follow HTML and CSS coding standards.