Safari 3.x calculates the documentHeight/documentWidth differently with or without scrollbars.
This page appears placing a div over the page and using Dom.getDocumentHeight/Width to set the size of it to cover the whole page. You will notice that there are scrollbars on the left and the bottom. Start resizing the window and you will see the scrollbars grow.
Now add ?patch=1 to the URL and it will be fixed.
Dom.getDocumentHeight/Width uses scrollHeight and self.innerHeight for Safari. But Safari 3.x needs document.documentElement.offsetHeight/Width to account for scrollbars.