User blog comment:DaNASCAT/Technical Update: October 25, 2011/@comment-1615275-20111025194521

On my home wiki, the wiki navigation (it's the advanced one) doesn't seem to be working quite correctly. If hacks are the problem, we are not using any hacks. The navigation, which is supposed to have four tab headings (other than "On the Wiki") only has three. It works well on the preview but once you click save, the fourth tab disappears.

I'm not sure if this is happening on other wikis, though.