HI everyone- anyone know how to use HTTP_REFERER from a pop up window?

I am using (javascipt):

<a class=link onClick ="return popup('email/email.asp?','Mailer',650,346)"
href="email.asp" onMouseOut="MM_swapImgRestore()"
onMouseOver="MM_swapImage('Image55','','images/email_friend_2.gif',1)"><img
name="Image55" border="0" src="images/email_friend_1.gif" width="96"
height="11"></a>


and VB Script (snippet)

 <%
Dim referingURL
referingURL = request.ServerVariables("HTTP_REFERER")
%>

refering URL is empty when written to the page?- (probably cos link not
properly specified on jscript for pop up??


Any ideas?

Cheers

Sam