function showlayer(id)
	{
 		if(document.all)
		{
	 		document.all["U_"+id].style.visibility = "visible";
		}
		else if(document.layers)
		{
			document.layers["U"+id].visibility = "visible";
		}
		else if(document.getElementById && !document.all)
		{
			document.getElementById("U_"+id).style.visibility = "visible";
		}
 	}
 	function hidelayer()
 	{
 		if(document.all)
		{
			for(i=1;i<=6;i++)
	 			document.all["U_"+i].style.visibility = "hidden";
		}
		else if(document.layers)
		{
			for(i=1;i<=6;i++)
				document.layers["U"+i].visibility = "hidden";
		}
		else if(document.getElementById && !document.all)
		{
			for(i=1;i<=6;i++)
	 			document.getElementById("U_"+i).style.visibility = "hidden";
		}
	}