Browser.display.focus ring on anything
From MozillaZine Knowledge Base
In Mozilla applications, focus is normally indicated by a dotted outline surrounding the element. By default, only a few elements visually indicate whether they have focus (links, form controls, etc.). When this preference is true, any focused element will display a focus ring around it.
Possible values and their effects
Display the focus ring around any and all focused elements (matched by the CSS selector
Limit the focus ring to the default set of focusable elements (matched by the CSS selector
First checked in
Has an effect in