Ok... so I made a little change to the last xslt (see below) in my
cocoon pipeline which adds the xhtml namespace on xsl:stylesheet level.

<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns="http://www.w3.org/1999/xhtml">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:template match="/">
<xsl:apply-templates/>
</xsl:template>
<!-- copy all nodes and attributes which are not processed by one of
available templates -->
<xsl:template match="@*|node()">
<xsl:copy>
<xsl:apply-templates select="@*"/>
<xsl:apply-templates/>
</xsl:copy>
</xsl:template>
<xsl:template match="escapeHtml">
<xsl:value-of select="." disable-output-escaping="yes"/>
</xsl:template>

</xsl:stylesheet>

	Martin Honnen
	http://msmvps.com/blogs/martin_honnen/