XSL tag validator

[paetje]

I'm using the following code to make some words in my text boldcode in XML

<nadruk> Bold </nadruk>

code in XSL

<xsl:template match="nadruk">	<span class="bold">  <xsl:apply-templates/>	</span>	</xsl:template>

and with CSS

.bold {	font-weight:bold;	}

this works just fine but now I want one central document to valide all the pages, on the way you do with an CSS file. Does anyone know how to make this kind of document and call it on my XSL page?