var leftnav = '';
function opend_leftnav(ElementId) {

	if (document.getElementById && (leftnav!=ElementId)) {
	
		if (leftnav!='')
			document.getElementById(leftnav).style.display = "none";
			
		document.getElementById(ElementId).style.display = "block";
		
		leftnav = ElementId;
	}

return false;
}