should be rendered as the characters (starting
with the ampersand and ending with the semi-colon) that
make up the entity reference.</li>

<li>When rendering content, User Agents that encounter 
characters or character entity references that are recognized but not renderable should display the document in such a way that it is obvious to the user that normal rendering has not taken place.</li>

<li>
The following characters are defined in [XML] as whitespace characters:

<ul>
<li>Space (&amp;#x0020;)</li>
<