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.
Translations:Handbook intro upc/1/en
This is the wiki area for the collaborative editing of the upcoming edition of the PC‑BSD® Users Handbook. If you are using STABLE or would like to assist in documenting the next release, refer to this wiki version of the Handbook. Otherwise, refer to the revision of the PC‑BSD® Users Handbook that matches your RELEASE version of PC‑BSD®.