Cybernetnews write about a cool Firefox cheat which would possibly stun your friends by embedding a Firefox window within a Firefox Window. Just enter this code into your Firefox address bar and hit Enter:
I tried it on my browser, it looked awesome, but the performance of the browser was not upto the mark. Anyways, who cares? You could try sneaking into your friendÃ¢â‚¬â„¢s browser and setting the above address as his homepage, it will surely drive him nuts!