function increaseheight(){
	if(document.getElementById('leftNav')) {
		var leftNav=document.getElementById('leftNav');
		var mainContent=document.getElementById('mainContent');
	
		if (leftNav.offsetHeight >= mainContent.offsetHeight) {
			mainContent.style.height = leftNav.offsetHeight +'px';
		} else {
			leftNav.style.height = mainContent.offsetHeight +'px';
		}
	}
}

window.onload=function(){ 
	increaseheight();
}