I have tried to reinstall it but it didn't worked, now i don't have any intellisence on the server controls only html and css in .aspx files.
Does some one know how fix it?!
Try to clear reflected schemas folder(of course backup it first :) ) and restart studio
On my Win Xp it on
C:\Documents and Settings\<UserName>\Application Data\Microsoft\VisualStudio\10.0\ReflectedSchemas