Using xsl:with-param without @name

xsl:with-param passes a value to a named parameter of the template, function, or mode it invokes. The @name attribute is what binds the value to that parameter, so it is required: without it the processor has no parameter to bind to and rejects the stylesheet.

Incorrect:

<xsl:call-template name="render">
  <xsl:with-param select="'red'"/>
</xsl:call-template>

Correct:

<xsl:call-template name="render">
  <xsl:with-param name="colour" select="'red'"/>
</xsl:call-template>