wordpress theme big footer problem

he on my network i created new site http://a2tips.bettingtip.info and see image what heppens when widget are is higher than content area.

Footer is raising up, up to bottom of comments, when content area is higher that widget area its ok, see http://a1tips.bettingtip.info

its not problem when i create sites, i will be carefull but when users start their own blogs there can be a lot of messages on my email with that problem, how it can be solved?