Sorry for the inconvenience. Known Navigation header breakage, its being "rebuilt."
There may be other unforeseen breakage primarily in the handbook portion of the wiki.
The Table Of Contents section of each "PC-BSD® Users Handbook" page may be the best workaround.
I was trying to get help so I used the left hand navigation and selected the last item I can see, Help. From there I selected Finding Help ( http://wiki.pcbsd.org/index.php?title=Finding_Help&action=edit&redlink=1 ) The page is gone!
All of the links at http://wiki.pcbsd.org/index.php/Finding_Help/10.1 should be there.
This is likely another of the pages which seldom change, and ought to be adjusted to reflect that. It simply has not been done yet, but yes, surely the "versioned" page exists. I was "away" for a while and plan to get back at task on whatever is needed for the wiki.. eventually have my own local copy once more for testing/experimentation and some evaluation of newer software etc.