Drupal: Navigation 404

gistfile1.php

<?php


/**
 * Implements hook_menu().
 */
function mymodule_menu() {
  $items = array();

  // PUBLIC PAGES
  $items['error404'] = array(
    'title' => "Page not found",
    'page callback' => 'mymodule_404_page',
    'access arguments' => array('access content'),
    'type' => MENU_SUGGESTED_ITEM,
  );
  $items['error403'] = array(
    'title' => "Access denied",
    'page callback' => 'mymodule_403_page',
    'access arguments' => array('access content'),
    'type' => MENU_SUGGESTED_ITEM,
  );

  return $items;
}


/**
 * Callback for 404
 * Mimic navigation404 module.
 */
function mymodule_404_page() {
  drupal_set_title(t("Page not found"));
  return t("The requested page could not be found.");
}

/**
 * Callback for 403
 * Mimic navigation404 module.
 */
function mymodule_403_page() {
  drupal_set_title(t("Access denied"));
  return t("You are not authorized to access this page.");
}