This page has a scrollbar that indicates the page is much longer than it really is. The bug appears to be due to a fixed position division inside another fixed position div that also has a z-index set. If the z-index is removed from the outside div, the scrollbar disappears.
Turning off the z-index reveals another bug - using the Javascript to move the inside div up/down leaves behind part of the text (about 1½ characters are not erased properly).
The amount of extra scrolling available is proportional to the distance the inside fixed div is from the top of the screen. In this case, the inside fixed div is at the bottom of the screen. If its bottom value was larger (pushing it up towards the top of the screen) the scrollbar would scroll less.
Use the following to adjust the position of the inside div: Move up / down.
It looks related to the Reverse Windowshade Bug.