unfortunately you still cannot expect css to look the same on every browser, even though the css-support is much better then some years ago.
you could check the browser with php on the serverside or with javascript on the clientside and deliver different css-files to the browser or even different html-code. but i would strongly recommend to code your html/css in a way that looks good on (almost) every browser without such a browser-switch.
always remember: html is not a textbased photoshop - so it's ok if your page doesn't look EXACTLY the same on different browsers, os' and displays.