One of the customization features of the DocBook XSL stylesheets is a set of empty XSL templates. These are placeholder templates that can be filled in by you. They are automatically called at particular points during processing, but by default they are empty and have no effect. If you fill them in, then they will have the effect you define.

For example, there is an empty template named user.header.content in the HTML stylesheet. It is called at the top of each HTML page generated during chunking. If you put some content in such a named template in your customization layer, then that content will appear at the top of every HTML output file. A trivial example is:

<xsl:template name="user.header.content">
  <p><b>Hi Mom!</b></p>
</xsl:template>

The template body can be any valid XSL coding that can generate whatever content you want. A more complete example of HTML headers and footers is in the section “HTML headers and footers”.