Local version works - production breaks

Hi, I have re-written a very basic website to use sessions (switching to https) for login to special areas of a site. After testing the site thoroughly locally, I uploaded the whole shebang to a unix server that runs Apache 1.3.x + PHP 4.3.4 + mysql. Almost all code broke - sessions would load, but almost every page was so messed up that -- well, I'm flabbergasted! I'm wondering, after reading a few threads on my local config whether the problem might lie with the Apache2 server I use locally (Mandrake special with Extranet). I also use an older version of PHP 4.3.1. I've examined both configs for differences, but can see nothing that would account for such an extremely messed up site. It loads locally beautifully (and all admin pages work) in Opera, Galeon, Mozilla, + Konqueror. Loads with errors to mysql db in all others but Konqueror which does not even display the opening page (yet I can view source). Maybe this isn't the forum to ask -- but seeing that all db access is through PHP -- I wonder whether anyone can point where i can start looking for the culprit(s). Any ideas, suggestions, or advice will be greatly appreciated. Tia, Andre