Absolutely-positioned elements that expand beyond the boundaries of the body seem to cause scrollbars to appear, for some reason. You can remedy this by simply wrapping everything inside the body tag in a relatively-positioned div styled with overflow: hidden;. The absolutely positioned content that expands beyond the boundaries of this container won’t cause scrollbars on the window.
Here’s a working example: http://jsfiddle.net/8UkQA/1/