Make divs equal height - Highest div wins
HTML
<div id="lol"></div>
<div id="rofl"></div>
CSS
#lol, #rofl { float: left; width: 200px; }
#lol { background: papayawhip; height: 100%; }
#rofl { background: green; height: 200px; }
JavaScript
var jQuerylol = jQuery('#lol'),
jQueryrofl = jQuery('#rofl');
if ( jQuerylol.height() > jQueryrofl.height() ) {
jQueryrofl.height( jQuerylol.height() );
} else {
jQuerylol.height( jQueryrofl.height() );
}