Sorry for the inconvenience. Known Navigation header breakage, its being "rebuilt" but forward nav should be ok now.
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.
Talk:Turn FreeBSD into PC-BSD®
Quite likely, I just don't know how to paste this url properly, but I have had conversion errors when pasting into lynx, ssh, and dumb terminals. Perhaps you could change the URL to be (R) instead of ®. I feel it would make it more accessible.