Remove -ms-linear-gradient that was only used by IE 10 preview releases.
Remove -o-linear-gradient used by Opera 11.1 - 12.0. These versions are now very rarely used.
Remove -khtml-user-select. It's not supported by KHTML anyways and their marketshare is incredibly minor.
Remove duplicate property.
Merge pull request #1628 from realityking/css

Cleanup CSS