I've been using my 24" iMac for an extended period of time today, and had firefox open in the background while i was working in adobe suite and iwork. at a later time i decided to boot into windows vista through bootcamp, and sat in there for about half hour. i then switched back to osx, and as it was booting up (where the white screen comes up with the apple logo) i noticed a burn-in type of effect at the top of the screen which was displaying osx's firefox outlines. after rebooting the system again the lines were still there. now the system has been on for about half hour, and the lines seem to be gone (i switched background to all white to make sure). i didn't see if the lines were there or not when it was booting into windows because i went afk for a brief period of time while the system was booting up. is this normal, or is there something wrong with the screen? edit: just checked again, with a blue and gray background, and the outlines are still there.