function popper(url,w,h,nam) 
{ 
 if (!url) return false;
 var breite=840; 
 if (w) breite=w;
 var hoehe=640; 
 if (h) hoehe=h;
 var positionX=((screen.availWidth / 2) - breite / 2); 
 var positionY=((screen.availHeight / 2) - hoehe / 2); 
 var pname = url;
 if (nam) pname = nam;
 pop=window.open('',pname,'toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0,resizable=1,fullscreen=0,width='+breite+',height='+hoehe+',top=0,left=0'); 
 pop.resizeTo(breite,hoehe); 
 pop.moveTo(positionX,positionY); 
 pop.location=url; 
 pop.focus();
 return false;
 }