This problem is totally boggling my mind. I have a new website, with 5 main pages, all but one of those pages has an unexplained gap beneath the footer, but only in firefox. I say unexplained because I used firebug to determine that it's not an element or the padding/margin of any elements.
I validated all of the pages in HTML and CSS3, and they all checked out so I don't think it's a broken tag.
I'd be greatfull if someone could poke around with firebug and check it out...
a page with the unexplained space: http://www.smorecreative.com/about/ the page without the unexplained space: http://www.smorecreative.com/work/
I tracked your problem down to the following code - If you remove this block of code, the mysterious gap goes away... But I don't know why Firefox doesn't like this code, and the other browsers are happy with it.
<script type="text/javascript">
// Pretty Checkboxes
jQuery(document).ready(function(){
jQuery('input[type=checkbox]').prettyCheckboxes();
});
</script>