// show or hide layers
 function showhide(id){
   if(document.getElementById(id).style.display == 'none') {
     document.getElementById(id).style.display = 'block';
   } else {
     document.getElementById(id).style.display = 'none';
   }
 }
 function show(id){
   document.getElementById(id).style.display = 'block';
 }
 function hide(id){
   document.getElementById(id).style.display = 'none';
 }

 // open pop up window
 function openwindow(url,breite,hoehe){
	var url;
	var width=breite;
	 var height=hoehe;
	 var l = (screen.availWidth - width) / 2;
	 var t = (screen.availHeight - height) / 2;
 	newwindow = window.open(url,"newwindow","width="+breite+",height=" +hoehe+",screenX="+l+",screenY="+t+",left=" +l+",top="+t+",scrollbars=1,resizable=0,menubar=no");
 	newwindow.focus();
 }