function popup(h,w,url)
{
  h = h - 20;
  var x=0, y=0, parameter="";
  if (w < screen.availWidth || h < screen.availHeight)
  {
    x = (screen.availWidth - w - 12) / 2;
    y = (screen.availHeight - h - 104) / 2;
    if (window.opera) y = 0;
    if (x<0 || y<0)
	{
	  x=0; y=0;
	}
    else parameter = "width=" + w + ",height=" + h + ",";
  }
  parameter += "left=" + x + ",top=" + y;
  parameter += ",menubar=no,location=no,toolbar=no,status=no";
  parameter += ",resizable=no,scrollbars=no";
  var popupWindow = window.open(url,"Galerie",parameter);
  if (popupWindow) popupWindow.focus();
  return !popupWindow;
}