 type <code>ID</code> is much smaller than
for those of type <code>CDATA</code>, the type of the <code>name</code>
attribute has been changed to <code>NMTOKEN</code>. This attribute is
constrained such that it can only have the same values as type
<code>ID</code>, or as the <code>Name</code> production in XML 1.0 Section
2.5, production 5. Unfortunately, this constraint cannot be expressed in the
XHTML 1.0 DTDs.  Because of this change, care must be taken when
converting existing HTML documents. The values 