my 3gs seems to have a dead pixel in the bottom right hand corner of my screen, or at least that's what i think it is. it's not noticeable on a bright screen, but when the screen goes dark, for instance, when i'm starting apps, it's hella noticeable. is this normal? or if not, would this be enough reason to get it exchanged? i know it might seem like a tiny problem, but this is my first iPhone and I want it to be perfect.