REXML could not parse this XML/HTML: 
<xsl:if test="not(sitemap:urlset/sitemap:url)">
  <p>Stylesheet for the <a href="/sitemap.xml">Sitemap</a></p>
  <style>
    #urlset {display: none;}
  </style>
</xsl:if>

REXML could not parse this XML/HTML: 
<table id="urlset" cellpadding="5">
	<tr style="border-bottom:1px black solid;">
		<th>URL</th>
		<th>Priority</th>
		<th>Change Frequency</th>
		<th>LastChange (GMT)</th>
	</tr>
	<xsl:variable name="lower" select="'abcdefghijklmnopqrstuvwxyz'"/>
	<xsl:variable name="upper" select="'ABCDEFGHIJKLMNOPQRSTUVWXYZ'"/>
	<xsl:for-each select="sitemap:urlset/sitemap:url">
		<tr>
			<xsl:if test="position() mod 2 != 1">
				<xsl:attribute name="class">high</xsl:attribute>
			</xsl:if>
			<td>
				<xsl:variable name="itemURL">
					<xsl:value-of select="sitemap:loc"/>
				</xsl:variable>
				<a href="{$itemURL}">
					<xsl:value-of select="sitemap:loc"/>
				</a>
			</td>
			<td>
				<xsl:value-of select="concat(sitemap:priority*100,'%')"/>
			</td>
			<td>
				<xsl:value-of select="concat(translate(substring(sitemap:changefreq, 1, 1),concat($lower, $upper),concat($upper, $lower)),substring(sitemap:changefreq, 2))"/>
			</td>
			<td>
				<xsl:value-of select="concat(substring(sitemap:lastmod,0,11),concat(' ', substring(sitemap:lastmod,12,5)))"/>
			</td>
		</tr>
	</xsl:for-each>
</table>