function init_page( ) {
  // png fix
  if ( typeof(pngfix) == 'function' ) {
    pngfix();
  }
}

function open_window( url, width, height, extra_params ) {
  extra_params = extra_params || 'dependent=no,directories=no,location=no,menubar=no,personalbar=no,status=no,resizable=yes,scrollbars=no';
  width  = width  || 450;
  height = height || 600;
  window.open( url, 'popupWindow', 'width='+width+',height='+height+','+extra_params);
}