http://weblogs.asp.net/avnerk/archive/2007/09/03/visual-studio-help-launcher-rant.aspx

How to disable the F1 keyboard shortcut for on-line help in Visual Studio.

That's one thing about Visual Studio that has sucked for a very, very long time (over a decade).  It's to the point where it could be considered a great feature if they improved the on-line help experience.