> <xsl:variable name="filepath" select="C:/webserver/htdocs"/>
> <input type="image" 
> src="<xsl:value-of select="$filepath"/>/Images/back.gif"
> onclick="history.back()"/>

You can use curly braces (attribute value templates) in cases as these: 

src="{$filepath"}/Images/back.gif"

Linda


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