[Skalman]

Such a simple idea - but it does make it easier to follow. The only problem I have is that it's very mac-centric. On my system the focus color is orange and it looks a bit off.

I'd suggest to use the highlight color:

  box-shadow: 0px 0px 2px 3px highlight, 0px 0px 2px highlight inset

[NVI]

Unfortunately, this will make colors look off on OS X. "highlight" color is different from the focus color on OS X.

Hardcoding colors for different OS-s might be more reliable.

[Skalman]

Oh, didn't know. You could even force highlight colors, by explicitly setting border or outline colors.

[thomasahle]

And different OS themes... And updating the list every time they change...

[rorrr2]

I doubt you can detect an OS theme with Javascript or CSS.

[Skalman]

You can actually partially detect it with Firefox.

https://developer.mozilla.org/en-US/docs/Web/CSS/:-moz-syste... https://developer.mozilla.org/en-US/docs/Web/CSS/:-moz-syste...