Returns a string of the date (but not the time) that the server (or local filesystem) reports the currently-loaded file was most recently modified. IE 4's value is a long date format, but starting with IE 5, the date information is formatted as mm/dd/yyyy. The value may be corrupted or incorrect if the server supplies the data in a format that IE does not expect. Implemented in IE 5/Mac, but the value is empty.