outline CSS property provides visual indicators as to which element is
currently selected within a web page. These are the dotted lines you see
surrounding links, etc. when you tab to them using the keyboard.
These indicators are important for users navigating without a mouse (such as
those with visual or mobility impairments). Setting
outline style to
0 removes these indicators, leaving these users without any way to tell
where they are within the page, therefore making the page inaccessible.
outline is not the only way to emphasize selected elements. You may
instead choose to change the background color, add an underline, or otherwise
make them visually distinct. Learn more & get alternative suggestions at
Suppress false positives by adding the suppression annotation
@SuppressWarnings("OutlineNone") to the enclosing element.