I have found these error messages in XenForo's phrases: Please enter a valid admin navigation link ID. Please enter a valid admin navigation section ID. Please enter a valid admin navigation tab ID. However there are no link IDs, section IDs and tab IDs for the admin navigation in the ACP. There is only a normal admin navigation ID, whose error message is used in library/XenForo/DataWriter/AdminNavigation.php. So what's the reason for putting those messages in xenforo when they are not used at all?