fenster = null;

function showpano(name)
{
  if(fenster != null)
  {
    if(!fenster.closed) {fenster.close()};
  }
  fenster = open(name,"Panorama","width=850,height=680,menubar=no,status=no,scrollbars=yes,resizable=yes,locationbar=no");
  fenster.focus();
};