The Multitasking Gestures in iOS 4.3 are an incredible feature

[Maaz]

You can't do this but I recommend downloading the iCab browser...it includes this functionality even if it can be slightly buggy sometimes.

Or atomic browser

 

[zhenya]

Or atomic browser

Neither of which can access the new javascript engine.

 

[neko girl]

FYI, this can be done on a non-paid-for Xcode 3.2.5. Takes less than a minute to do..