Well as i surfed the web i came across this nice article:

http://weblogs.asp.net/ssharrock/archive/2003/04/20/5875.aspx

A little bit late but it shows you this tip:

Just two simple steps to client-side debugging nirvana.
  1. Clear the "disable script debugging" checkbox in Internet Explorer's advanced properties.
  2. Add the keyword "debugger" somewhere within your JavaScript.

And VS will launch and enable you to debug your script as you were debugging C#.

Greate Feature Thx VS Guys :)

Happy Debugging