[serialization] XHTML output method

Hi,

Section 5 XHTML Output method:

"The serializer should output namespace declarations in a way that is
consistent with the requirements of the XHTML DTD if this is
possible. The DTD requires the declaration
xmlns="http://www.w3.org/1999/xhtml" to appear on the html element,
and only on the html element."

The first 'should' should be a 'must' or it would make the statement
allow serialisations that are not XHTML. XHTML1 says:

"The root element of the document must contain an xmlns declaration
for the XHTML namespace [XMLNS]."

Cheers,

Max.

PS. all the examples of minimised elements are written with 2 spaces,
as in "The serializer should include a space before the trailing />,
e.g. <br  /> "