If your screen is narrower than 1100px then the ad that is otherwise shown on the right-hand side doesn't appear at all. If your screen is wider than that then the ad will appear, but on a screens only a little wider, say 1280 px, the banner will appear 'cut off'' as there isn't enough room for it to display fully. If you scroll all the way to the bottom of the page then you should see a scrollbar which allows you to navigate right and view the banner. There's no way to do anything about that without a fundamental redesign of the site.