Well this should be a good day form Mac browsing. There's a leaked v64 build of Safari (which includes tabbed browsing, and from first glance seems to solve the bizarre connectivity issue I was having), and Camino 0.7.
Followup: Safari v64 completely chokes on the Industrie Toulouse style sheet, whereas v51 handles it fine. v64 handles Chris' site fine though. Hmmm. I wonder what I've got going wrong.
Followup followup: Bringing the stylesheet into BBEdit 6.5 and having BBEdit automatically reformat it seemed to do the trick.
Followup followup followup: I still have the connectivity issues to Roundup. :(