"Web accessibility refers to the practice of making websites usable by people of all abilities and disabilities. When sites are correctly designed, developed and edited, all users can have equal access to information and functionality" (from http://en.wikipedia.org/wiki/Web_accessibility).

WCAG

"The Web Content Accessibility Guidelines are part of a series of web accessibility guidelines published by the Web Accessibility Initiative of the World Wide Web Consortium, the main international standards organization for the Internet." (https://en.wikipedia.org/wiki/Web_Content_Accessibility_Guidelines).

Section 508

Every United States federal website must be in compliance with the country’s accessibility laws which are codified in Section 508 of the Rehabilitation Act of 1973, revised in 2018. The GSA maintains a list of specific technical requirements for a website to be 508-compliant. They are nearly synonymous with the WCAG 2.1 Level AA criteria.

Tiki isn't currently WCAG 2.1 compliant, and examination of Tiki website pages with a tool like the WAVE browser extension turns up numerous errors. Making the necessary changes throughout the code for full WCAG 2.1 compliance is on the Tiki development roadmap, coinciding with the upgrade to version 5 of the Bootstrap layout framework in Tiki 25, to be released in October 2022. In the meantime, it may be possible to be compliant for a specific project with a custom theme and editing most-used files.

Compliance with WCAG 2.1 as soon as possible is a priority for Tiki code development. For projects where this is required now or in the immediate future, accessibility shortcomings can be addressed in two ways. First, the visual theme can be designed so that there are no text readability issues due to insufficient color contrast. This is a common problem and is relatively easily rectified, and can be done on the project level. Second, WCAG noncompliance errors also stem from HTML issues. To minimize these for a particular project, the specific files used by the project can be identified and the issues in them resolved (the actual fixes are quite simple).

• https://www.w3.org/WAI/WCAG21/quickref/
• https://www.w3.org/TR/UNDERSTANDING-WCAG20/conformance.html - Differences between Level A and AA, etc.
• https://www.aoda.ca/web-accessibility-guidelines-for-preventing-online-barriers/
• https://aoda.ca/what-is-the-information-and-communications-standards/
• https://www.aoda.ca/aoda-website-accessibility-audit/
• https://section508.gov/content/guide-accessible-web-design-development - For United States federal government websites
• https://www.section508.gov/test/web-software
• https://developer.mozilla.org/en-US/docs/Web/Accessibility/An_overview_of_accessible_web_applications_and_widgets
• https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA - "a set of attributes that define ways to make web content and web applications (especially those developed with JavaScript) more accessible to people with disabilities."

Related: Browser Compatibility