var swidht=$('header').getWidth()-$('left_nav').getWidth()-$('right').getWidth()-20;

$('content').setStyle({width: swidht+'px'});

var leftH=$('left_nav').getHeight();
var rightH=$('right').getHeight();
var conH=$('content').getHeight();

if (conH>leftH)
{
	$('left_nav').setStyle({height: conH+'px'});
}

if (conH>rightH)
{	
	$('right').setStyle({height: conH+'px'});
}