I am a professional webdeveloper for many years and IMHO the best way is to look in your tacking tool and test in everything which has more than say 5% of your

I am a professional webdeveloper for many years and IMHO the best way is to look in your tacking tool and test in everything which has more than say 5% of your traffic in the last months. Browser usage varies strongly from the type of customer you have.