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.
Applications Selection Screen
(Sorry for the inconvenience)
The Sources Selection screen, seen in Figure 3.8a, allows advanced users to install FreeBSD source or the FreeBSD ports collection. These can also be installed after installation using the "System Tasks - Advanced Users" section of Control Panel ➜ System Manager ➜ Tasks.
Figure 3.8a: Sources Selection Screen
Highlight the FreeBSD component that you would like to install in the "Available" box and click the blue > button to add it to the "Selected" box. If you change your mind, highlight the item in the "Selected" box and click the blue < button. Whatever shows up in the "Selected" box when you click the Next button, will be installed for you.