Customizing stylesheet

Hi everybody!

I write a little stylesheet. In this stylesheet I imported the docbook 
stylesheets.I integrated the new stylesheet in my build.xml.

<xsl:import 
href="./docbook_config/docbook-xsl/docbook-xsl-ns-1.76.1/fo/docbook.xsl" />

Now I want to overide several things but it does not work!Can somebody help?

<!--margin left-->

	<xsl:param name="page.margin.inner">2cm</xsl:param>
	<xsl:param name="page.margin.top">3cm</xsl:param>
	<xsl:param name="page.margin.bottom">2cm</xsl:param>

<!--header-->

          <xsl:apply-templates select="." mode="object.title.markup"/>
    	 <xsl:attribute-set name="header.content.properties">
    	 <xsl:attribute name="font-family">Arial</xsl:attribute>
  	 <xsl:attribute name="font-size">9pt</xsl:attribute>
   	<xsl:attribute name="font-weight">bold</xsl:attribute>
   	</xsl:attribute-set>

<!--font-->

   	<xsl:param name="body.font.family">Arial</xsl:param>

     	<xsl:attribute-set name="section.title.properties">
     	<xsl:attribute name="font-family">Arial</xsl:attribute>
   	<xsl:attribute name="font-weight">bold</xsl:attribute>
   	</xsl:attribute-set>
   	
<!--line spacing-->
   	<xsl:attribute-set name="root.properties">
   	 <xsl:attribute name="line-height">normal</xsl:attribute>
   	</xsl:attribute-set>

-- 
Gruß Lwam Berhane

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