var fenster;
var param1 = param2 = "menubar=0,toolbar=0,personalbar=0,location=0,directories=0,resizable=1";

if (window.screen && window.screen.availWidth && window.screen.availHeight) {
  param1 += ",scrollbars=1,left=50,top=50,width=" + (window.screen.availWidth-100) + ",height=" + (window.screen.availHeight-100);
  param2 += ",left=" + (window.screen.availWidth/2-385) + ",top=" + (window.screen.availHeight/2-265) + ",width=770,height=530";
}

function popup(art, adr) {
  if (fenster && !fenster.closed)
	fenster.document.location.href = adr;
  else
	fenster = window.open(adr, false, art == 1 ? param1 : param2);
  fenster.focus();
}