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.
Post Installation Configuration and Installation Troubleshooting/9.2
Once PC-BSD is installed, the installer will allow you to configure your system at first boot.
This section describes the following post-installation screens: