Javascript to determine browser to load CSS?

I was just wondering if there is a way to load a CSS file depending on the browser that you are using. In this case I am looking to load a CSS file for Safari only. maybe another option would be to use CSS hacks (but not webkit). Any help would be appreciated.

Thank you

How do you plan on identifying that the browser is Safari? What does it handle differently from all other browsers that you can use to identify that the browser actually is Safari and not IE or Firefox pretending to be Safari?