Accessibility resources free online from the international standards organization: W3C Web Accessibility Initiative (WAI).| Web Accessibility Initiative (WAI)
Understanding Test Rules for WCAG 2 Success Criteria| www.w3.org
Technique G195:Using an author-supplied, visible focus indicator| www.w3.org
Technique G165:Using the default focus indicator for the platform so that high visibility default focus indicators will carry over| www.w3.org
Technique G149:Using user interface components that are highlighted by the user agent when they receive focus| www.w3.org
Styles defined with the regular :focus pseudo-class are applied whenever an element has focus, regardless of how it received focus. In contrast, user agents apply additional heuristics and logic to decide when to show :focus-visible styles – in particular, browsers always show these styles when a user is navigating using the keyboard, but will generally not show them as a result of a mouse/pointer interaction (with the exception of elements that also support keyboard input, such as <input> ...| www.w3.org
Description| www.w3.org
Example 1: Link elements| www.w3.org
Technique SCR31:Using script to change the background color or border of the element with focus| www.w3.org
Using a solid outline| www.w3.org
Understanding Techniques for WCAG 2.2 Success Criteria| www.w3.org