Depending on elements and browsers, focus may not be visualized by default even if focus is received. It is a good idea to grant outline explicitly by CSS.
|Principle||Operable||User interface components and navigation must be operable.|
|Guideline||Navigable||Provide ways to help users navigate, find content, and determine where they are.|
|Every user interface capable of operating the keyboard has an operation mode in which the focus indicator can be seen.|