"Keyboard trap" is an implementation that makes it impossible to escape from keyboard operation when focus shifts to an element. When creating a modal window etc., you have to be able to do it not only with the mouse but also with the keyboard to close it.
|Principle||Operable||User interface components and navigation must be operable.|
|Guideline||Keyboard Accessible||Make all functionality available from a keyboard.|
|Criterion||No Keyboard Trap
|If the keyboard interface can be used to move the keyboard focus to a component of the webpage, it is possible to remove focus from that component using only the keyboard interface. Furthermore, if you can not remove focus by using arrow keys without a modifier key, Tab key, or other standard method of removing focus, the user is notified of the method of removing focus.|