How to reproduce :

• use the skin "Demo"
• in the webapp\cms\skins\demo\newsletter\default\stylesheets\template.xsl, there is some params :

  <xsl:param name="contextPath"/>
  	<xsl:param name="skin"/>
  	<xsl:param name="siteName"/>
  	<xsl:param name="lang"/>
  	<xsl:param name="mail"/>
  	<xsl:param name="categoryTitle"/>
      <xsl:param name="title"/>
      <xsl:param name="number"/>
      <xsl:param name="date"/>

• add this line in the template :

  sitename = <xsl:value-of select="$siteName" />

• in preview, the value of the param siteName is empty.