Hail BjOrn, I'll tell you the answer if you and your vikings don't plunder or pillage my web site:
you'll find what you need here:
http://www.php.net/manual/en/function.get-browser.php
its about the global var $HTTP_USER_AGENT. Its an array of goodies, in the form of an array. the particular thing that will interest you are the keys "majorver" and "minorver".
So if yer new,
$HTTP_USER_AGENT["majorver"]
for IE5.0 will equal "5", minoerver will equal "0"
