Hi i have mac os x mountain lion the latest update, how do i install kde, i'm trying to create a website, i've use kde while at university but dont know how to download it on my mac

I would suggest looking into Macports or Fink, which should provide a certain version of KDE that you can install.
Be aware that the KDE workspace itself likely will not function completely on Mac OS X, but the applications themselves should work fine if you get it working.

Precompiled binaries are not available to the best of my knowledge - Macports and Fink will allow you to compile it in a fairly automated manner however.