CSS rendering problem

hi…
i am facing very common problem in css layout design…
the page that i m trying to get thruough IE6 and FF under Win.
i m using three column layout as illustrated in alistapart.
when i put some content formed with <ul>'s and <div>'s in the content area, IE6 gets the footer thouching the contents length, instead of clearing all three column and stay at bottom…

what i m looking for is some causes that might lead to this…i hope i m asking too much without example of the code but i cant right now expose it…i hope this makes some sense…
:puzzled: