What is better: CSS hacks or browser detection?

Question

Commonly when I look around the Internet, I find that people are generally using CSS hacks to make their website look the same in all browsers. Personally, I have found this

Answer 1

Whats wrong with detecting the browser server side? Seems very effective and foolproof (save for the user altering their user-agent string). You can use PHP to either choose the stylesheet for a page or dynamically generate it for each request - not sure if other languages let you output directly to the file and let you set the headers manually, but I can't imagine them not letting you identify the user-agent, so one of these options is probably viable for any server-side environment.