> 		<xsl:variable name="tif" select="col/@physname"/>
> 			<a href="$tif">  <!-- here the error 
> takes place -->

Do

  <a href="{$tif}">

or simply

  <a href="{col/@physname}">

See http://www.w3.org/TR/xslt#attribute-value-templates for more info.

Jarno

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list