function submit_login_form($form)
 {
     $auth = node::authenticate_node($form['fields']['username']['value'], $form['fields']['password']['value']);
     if ($auth) {
         $_SESSION['SERUM_AUTHENTICATED'] = true;
         $_SESSION['ACTIVE_NODE_ID'] = $auth->id;
     } else {
         //Send error message back to browser.
         $_SESSION['SERUM_AUTHENTICATED'] = false;
         serum_set_message('Authentication Failed.', $type = 'status');
     }
     header('location: ' . base_path());
 }