var pop = null;
function popdown() {
  if (pop && !pop.closed) pop.close();
}
function aufpoppen(obj,w,h) {
  var url = (obj.getAttribute) ? obj.getAttribute('href') : obj.href;
  if (!url) return true;
  w = (w) ? w += 20 : 150;  // 150px*150px is the default size
  h = (h) ? h += 25 : 150;
  
  //Zentrieren
  var padding;
   (navigator.appName == "Microsoft Internet Explorer") ? (padding = 10) : (padding = 0); 
  var screenw = screen.availWidth;
  var screenh = screen.availHeight; 
  var winw = (w + 15 + padding);
  var winh = (h + 15 + padding); 
  var posx = (screenw / 2) - (winw / 2);
  var posy = (screenh / 2) - (winh / 2);
  
  var args = 'width='+w+',height='+h+',resizable,scrollbars,top='+posy+',left='+posx+'';
  popdown();
  pop = window.open(url,'',args);
  window.name = "popupfenster";
  return (pop) ? false : true;
}

function mach(sichtbar)
{
	sichtbar.style.display = (sichtbar.style.display == 'none')?'':'none'; 
	return false;
}