function chkheight(){
	var layerCol1 = document.getElementById("sidebar-a");
	var layerCol2 = document.getElementById("midcol");
	var layerCol3 = document.getElementById("sidebar-b");
	var col2height = layerCol2.offsetHeight;
	var col1height = layerCol1.offsetHeight;
	var col3height = layerCol3.offsetHeight;
	var maxheight = col1height;
	if(col2height > maxheight){
		maxheight=col2height;
	}
	if(col3height > maxheight){
		maxheight=col3height;
	}
	layerCol1.style.height=maxheight;
	layerCol2.style.height=maxheight;
	layerCol3.style.height=maxheight;
}