http://onlinehandytools.com/blah.php?board=EDE&level=AL&subject=biology&year=2011
If you click on any of the links labeled QP/MS in Firefox/Opera the iframe won't take up the full height and only takes up about 10% of the height. Not sure why this is happening as it's working perfectly fine in Chrome.
You have only given the table those iframes are sitting in height:100% – but that doesn’t mean the elements inside the table have to take that height as well.
Give the tbody, tr and td elements inside that table the same height as well.