function openWindow(pfad,name,breite,hoehe,prop){
  xpos=(screen.width-breite)/2;
  ypos=(screen.height-hoehe)/2;
  prop+=(prop!='')?',':'';
  prop+=',left='+xpos+',top='+ypos;
  F1=window.open(pfad,name,prop+((prop!='')?',':'')+'width='+breite+',height='+hoehe);
}