twitter/twitter.github.com — Issue #1: Use :after instead of ::after
Author: necolas
Created: 2012-01-30 22:35:31+00:00
State: open

https://github.com/twitter/twitter.github.com/blob/master/assets/style.css#L176

IE doesn't support `::after` but it does support `:after`. All modern browsers must support both notations, so you're better off using the earlier, single-colon notation for wider browser support.