Changing the setting of any user interface element shouldn't cause an automatic change of context, unless the user has been notified of the behavior before they use the element. "Change of context" in this sense means "major changes in the content of the Web page that, if made without user awareness, can disorient users who are not able to view the entire page simultaneously". This could include changes of user agent, of viewport (usually the active window), of focus, or of content that changes the meaning of the page.
3.2.2 On Input: Changing the setting of any user interface component does not automatically cause a change of context unless the user has been advised of the behavior before using the component. (Level A)
How to fix:
Setting a form elements (as opposed to activating a link, or using a submit button to explicitly submit a form shouldn't change the page context, unless the user is advised ahead of time.
- Rather than changing the window.location when a select element is changed, add a submit button, so that the user can activate the location change explicitly.
- Add explanatory text adjacent to the control. For example, a set of radio buttons for language selection could have some text indicating that the language will be changed as soon as the user makes a selection