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.
PC-BSD® Users Handbook/9.2
The revision #48492 of the page named "PC-BSD® Users Handbook/9.2/en" does not exist.
This is usually caused by following an outdated history link to a page that has been deleted. Details can be found in the deletion log.