Fix/overlay scrolling

A small bug, but it's sort of been bugging me when I have the console open.  If you scroll, you can scroll so the overlay is only partly covering the screen.
According to http://stackoverflow.com/questions/1628265/how-to-get-positionfixed-css-to-work-in-ie-7-with-transitional-doctype position:fixed should work on IE7 (but not IE6).