Sometimes, when you try to develop things that work in Internet Explorer, you get to a point where you can just scratch your head and wonder “what the he*$ where they thinking of?!?”. This is one of those cases:
This is in Internet Explorer 8 when set to IE7 mode, but this is very faithful to the original as I’ve tested it on a real IE7 and it behaves the same. What happens here is that when you scroll the page down, all absolutely positioned elements (the two “combo boxes” which are a custom UI widget and the text “Dimensions:… at the top right corner”) get pulled down a few pixels. When you scroll up, they get put back in the correct place.