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.
https://www.youtube.com/watch?v=ilj2P5-5CjI&index=1&list=PLNYkxOF6rcICWx0C9LVWWVqvHlYJyqw7g 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.
Check out the W3C/WAI Web Accessibility Tutorials, edited by yours truly with the enormous help of the Education and Outreach Working Group and the accessibility community.(about)