its either oil from your hands getting onto the lcd screen or pressure points on it, I'm not sure which most people seem to think it's pressure points base on my solutions that have worked I think it's oil. First thing to do is cover it with something to stop it from growing(packaging tape worked at least as well as a screen protector on my droid x). After that, it will very slowly decrease in size by itself. If you get it cold it will speed the process along.