This plugin sniffs users agents, and provides a set of theme options for a user to put browser-specific CSS styles. It's very easy to use, very simple, and very powerful. Go to Apparence and click on cssbyua. This FORK is for Universal Mobile to Codecanyon :
https://codecanyon.net/user/sherdleapps/portfolio?ref=sherdleapps for apply a specific css. Work on Firefox, I.E., Chrome, Opera and iphone.Special Thanks :bradparbs
Fork original project : CSSniffer -
https://fr.wordpress.org/plugins/cssniffer/