Dieser Hinweis befindet sich praktisch auf jedem Dokument des W3C <p>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in <a href="http://www.ietf.org/rfc/rfc2119.txt">RFC 2119.</a></p>