This was a SERIOUSLY DIFFICULT problem to nail down.
After most of an afternoon reloading and reloading and reloading a page in safari to determine why it wasn't properly reflecting not just CSS changes (which is understandable given safari+CSS+forms) but in fact entire great swathes of HTML code that safari point blank wasn't loading from the server, I finally figured out that W3 Total Cache was the culprit. I even went so far as to manually delete the entire Safari cache folder off my HD...nada. Loaded the same page darn page again and again.
No problem in Firefox; it faithfully sought out the latest file on the server.
I had begun to manually disable items in the W3TC debug window, with nothing working, when I opted at one point to clear the disk cache (a button at the top of the settings page).
Just like that Safari MAGICALLY SPRANG INTO ACTION, remembering for a minute that it was a browser, and that it should look to the server for guidance. Well not on W3TC's watch; evidently some kind of cache setting absolutely forbade even manual attempts at forcing the browser to request the latest version of a file (which you would think W3TC would know, given that the files on the server are being >>>MODIFIED. Ahem.).
Sorry guys, I just installed this plugin to speed up my site a little, not to enter a world of servers and caches D&D action. It seems to be a great plugin, but if the cache can't even figure out to steer a browser past its own rules when it KNOWS a file has just been changed SINCE the last cache was saved...well what can I tell ya.
Wow, what a long afternoon that was.