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.
2 revisions of this difference (50170 and 50800) were not found.
This is usually caused by following an outdated diff link to a page that has been deleted. Details can be found in the deletion log.