howdy the li is a html tag using in making lists, in this case the tabs, for some reason the style you are using seems to use different layout than the standard help page which has the links/tabs to the left of the content.
As for forumlist, i meant the list of forums in xenforo i believe its template is called forum_list
i believe the board itself is using later than 1.4 so the above code shouldnt cause errors, but the skin doesnt seem to be much higher than 1.2 (where as you say custom help pages were later i believe 1.4), and yep was a quick fix while i was at work, didnt have a time to look into what was causing the default selectors to be overrode. saw an issue like that once before and that was a dbtech addon from 1.1 when on 1.2 or higher so could be related to li on pre 1.2 skins once the softtware itself is ugraded 1.2 and beyond.
notice there some odd issues with the usercards too, the avatars seem to be on the div above the info, very curious.