Hi, Mike,

If what you did works, that's good enough, of course. However, doing it a 
bit differently might have some benefits for you.

Compare
<xsl:for-each select="page">
  <xsl:variable name="prev" 
select="preceding-sibling::page[position()=1]"/>
  <xsl:if test="not($prev) or @tab!=$prev/@tab">
    <!-- Process the nodes you selected here -->
  </xsl:if>
</xsl:for-each>

to
<xsl:for-each select="page[not(@tab=following::page/@tab)]">
  <!-- Process the nodes you selected here -->
</xsl:for-each>