public function setPageNotFoundErrorCode(int $page_not_found_error_code = 404) : CNabuDataObject
    {
        if ($page_not_found_error_code === null) {
            throw new ENabuCoreException(
                    ENabuCoreException::ERROR_NULL_VALUE_NOT_ALLOWED_IN,
                    array("\$page_not_found_error_code")
            );
        }
        $this->setValue('nb_site_page_not_found_error_code', $page_not_found_error_code);
        
        return $this;
    }