I like how it underlines whether it's CSS or PHP too :P, and the link to the source at the bottom. Very handy little tool. Did it take long to make?
I wouldn't have clicked it until looking for a back button. Might be worth leaving it as text, and maybe placing a back button to the left of it? Personally I think something similar to the back button in Windows Phone would look nice. Something like the button here: http://i.msdn.microsoft.com/dynimg/IC505392.png