pported by a
Conforming User Agents.</dd>

<dt>Should</dt>

<dd>With respect to implementations, the word "should" is to be
interpreted as an implementation recommendation, but not a
requirement. With respect to documents, the word "should" is to
be interpreted as recommended programming practice for documents
and a requirement for Strictly Conforming XHTML Documents.</dd>

<dt>Supported</dt>

<dd>Certain facilities in this specification are optional. If a
facility is supported, it behaves as specified by t