3.2.1 Non-Conformance Shown with Non-Technical Explanation
If the users place focus on an element (tabbing to it via the keyboard or clicking on it with the mouse) and a context change occurs automatically without warning, that element is non-conforming. Do not have a keyboard tab or mouse click initiate a change without warning.
3.2.1 Non-Conformance Shown with Technical Explanation and HTML coding
No specific markup is required to inform users about context changes.