Great video over at the Google Chrome Developers channel about the upcoming CSS Level 4 :focus-ring selector (draft). The focus is often removed for stylistic reasons when using the mouse, but then keyboard users also have no indication of where they are on the website. :focus-ring solves that issue.

Focus Ring! -- A11ycasts #16

The video includes a shout out to this handy polyfill on Github. There are other videos about accessibility, also presented by Rob Dodson, available on the channel as well. Captions are available.