User blog comment:DaNASCAT/Technical Update: July 5, 2011/@comment-1656630-20110706163752/@comment-802147-20110707182152

Somehow, the background color (in the Theme Designer) is used for the background color for the "border" around the thumbnails. Since the Dragon Age wiki and Assassins's Creed wiki use transparent background, it looks extremely weird.

To remove it:

.WikiaArticle .tright, .WikiaArticle .tleft { outline: inherit }

I've made the changes for the Dragon Age wiki, so my example is no longer relevant heh.