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:What's New Since 9.1/9/en
- The GDM login manager has been replaced with the BSD-licensed PCDM.