function popupwindow(url,breit,hoch,center)
{
	if (center = true){
		links = (screen.width / 2) - (breit / 2);
		oben =(screen.height / 2) - (hoch / 2);
	}else{
		links = 0;
		oben = 0;
	}
  if (typeof scroller == "undefined")  scroller = 'no';
	breit = breit + 30;
	hoch  = hoch + 50;
	parameter = 'width='+breit+',height='+hoch+',toolbar=0,location=0,directories=0,status=yes,scrollbars=yes,menubar=0,resizeable=yes';
  popup = window.open(url,'PopupFenster',parameter);
	popup.focus();
	popup.moveTo(links,oben);			
	popup.resizeTo(breit,hoch);	
}