Are you in standards mode?
PHP Code:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
IE doesn't have a strict standards mode, (they call it 'Almost Standards Mode') This doctype should get you as close as possible. If it still doesn't work, you will need to write some browser specific code, which a pain, but doable.