How do I fix small gap at top and on the left of iMac display? I have an iMac mid-2010 (11,3) that is showing a small gap at the top and left side of the screen in the built-in display. It is almost like the screen position is off, or the display is not being fully stretched. There used to be a way in System Preferences to change the screen position in older OSX versions, but that's since gone. 



I did just replace RAM, could that cause this? And is there a way to fix it?
I have the same model with replaced RAM as well. You can try this. Open system preferences and click on display/Scaled. Now set the display to a couple of different resolution values and then return to your desired value. If offset is still apparent, try a different resolution.