onload=function() {

	var divL = document.getElementById('colL').offsetHeight;
	var divR = document.getElementById('colR').offsetHeight;
	
	var height=new Array();
	height[0]=divL;
	height[1]=divR;
	
	// uniquement si div3 existe
	try
	{
		// do whatever you want with your getElementById here
		var div3 = document.getElementById('col3').offsetHeight;
		height[2]=div3;
	}
	catch(err)
	{
		// id does exist
	}
	
	// trie le array par nombre descroissant
	height.sort(function(a,b){return b - a})
	
	var maxHeight=height[0];

	//alert(height);
	
	// uniquement si div3 existe
	try
	{
		// do whatever you want with your getElementById here
		var div3 = document.getElementById('col3');
		document.getElementById('col3').style.height=maxHeight+"px";
	}
	catch(err)
	{
		// id does exist
	}
	
	document.getElementById('colL').style.height=maxHeight+"px";
	document.getElementById('colR').style.height=maxHeight+"px";
		
 }