In looking at Zebra theme trying to resolve a query in the forum, I noticed that the output for the footer was wrongly placed.
If you are not already aware, but this code...
<?php echo $OUTPUT->standard_footer_html(); ?>
...should be situated just above the page-footer closing </div> like so...
<div id="page-footer">
...
<?php echo $OUTPUT->standard_footer_html(); ?>
</div>
This is so that any debugging/performance info/validator output will fall imediately below the footer area and not midway cutting through other text you may have in the footer.
Thanks for listening
Mary