User blog comment:DaNASCAT/Technical Update: May 6, 2014/@comment-2112602-20140507141213/@comment-452-20140507184634

Yes, .picture-attribution was the class used in pages published yesterday, and .attribution is the class in pages published today.

Since cached pages still use the old thumb style, the .picture-attribution rule will have to be left for a while in order to remove it from both old and new pages.