this feature is only available in IE8, it’s important that web developers provide additional defense-in-depth and work to eliminate XSS vulnerabilities in their sites. Preventing XSS on the server-side is much easier that catching it at the browser" IE 8...

security and stability issues including a critical vulnerability involving memory corruption, a few high vulnerabilities with SessionStore and XSS using a chrome XBL, and a moderate vulnerability in chrome privilege escalation. The changes aren't quite as extensive...