The outline styles (that blue line around the outside of a focused element)
are an essential part of accessibility for users using keyboard to navigate
around, it indicates which element is in focus at a given time. Users can
choose to "click" them by just pressing the
Enter key in the keyboard, instead of
using the mouse.
These styles are less important for users using the mouse, usually having them enabled can be annoying.
Frontile includes a library based
in the proposed CSS
:focus-visible pseudo-selector. It adds a
to the focused element, but it only adds the class when
Shift + Tab, or an
arrow key is used to focus an element. If the mouse is used to focus, the class
will not be added (with the exception of input and textarea elements).