function popup(url, navn, bredde, hojde, params)
{
  var popwin;

  pos_horizon = ((screen.width/2)-(bredde/2));
  pos_vertical = ((screen.height/2)-(hojde/2));
  var opts = "width="+bredde+", height="+hojde+", top="+pos_vertical+", left="+pos_horizon +", "+params;

  popwin = window.open("", navn, opts);
  popwin.focus();
  popwin.location = url;

  return false;
}