Hi, Can anyone help? I have had my Imac for about a year now ( iMac10,1. 3.06 GHz processor, NVIDIA GeForce 9400). I have just noticed the display seems to have dropped about 3-4mm, Giving me a black line above the menu bar and the dock lower at the bottom of the screen. My old PC and monitor had an option of shifting this. Does the Mac have anything like this? Thanks in anticipation.