$(document).ready(function() { 
var columns = $('#main_content,#sub_content').get().sort(function(a, b) {return $ 
(b).height() - $(a).height();}); 
var highest = columns[0]; 
$(highest).css({position: "relative"});
/* NOTE - The line below adds {height:100%} to div#sub_content AFTER {position:relative} has been applied by the script above, so the background image of the sub_content div extends all the way to the bottom of the column */
$("div#sub_content").css({height: "100%"});
});