Forum:Why is one Ad in a fixed position?

Hello, I'm asking why is one of the ads in this page, and the rest of the similar articles in Wikia when viewed as an anon are in a fixed position?

Can't we utilize the usable space below the sidebar? Will it be a violation of the Wikia's Terms of Use if the ad gets covered? Mckrongs 22:59, November 8, 2011 (UTC)