User blog comment:BertH/Fluid layout has arrived/@comment-24095203-20131208151357/@comment-452-20131210030313

I also see the second scrollbar on that wiki.

I poked around at their CSS, and it's indeed their site CSS that is the problem. It looks like whoever made it had no idea what they were doing.

You need to tell the admins of that wiki that they need to fix the problem.