XSS attacks are really common and a lot of the biggest sites have had or have issues with XSS - the involved sites include Gmail, PayPal, Facebook, Hotmail and lately Twitter. Being a lead developer of a popular site I'll share some of my experience on how to fix and prevent these malicious exploits. I'll also share a little insight on Twitter's latest exploit.
REFERENCE
http://amix.dk/blog/viewEntry/19432