In some browsers, the right-hand bar of the theme is sometimes placed at the very bottom of the page. It is possible that Internet Explorer displays the error, while in Firefox or Chrome everything is fine.
The mistake is often that HTML banners are used. These banners are too wide, or do not contain any width, so that they do not fit in the reserved space. You need to use your HTML banners with a maximum width of 190px, in order to prevent the rightbar from being moved.
It is also possible that own HTML in a modular page is too wide, and therefore the right bar 'pushes down'.