function loadSite(siteName) {
  disableForm();
  var parameters = {
    /* SOME PARAMETERS */
  };

  new Ajax.Request('ajax/ajax_db_execute.php', {
     method: 'post',
     parameters: parameters,
     onSuccess: callbackFunc
  });
}

function callbackFunc(transport) {
  response = transport.responseText.evalJSON(true);
  if(response.retcode === 0) {
    window.location = "start.php?id=<?php echo $id; ?>";
  } else {
    show_error_box(response.errortext);
      enableForm();
  }
}