Firefox displayed this warning in the Firebug console. This warning indicates an absolutely positioned does not consider a table element relatively positioned so it may not appear as expected. A better explanation is here:
https://www.sencha.com/forum/showthread.php?289315-Relative-positioning-of-table-rows-and-row-groups-is-now-supported.-This-site-may-nee
and solution to fix is here:
http://stackoverflow.com/questions/5148041/does-firefox-support-position-relative-on-table-elements