see:

NOSCRIPT.

You can put it in the HTML header, but not the HTTP header.

Update: Here's an example:

#!/usr/bin/perl

use strict;
use warnings;

print <<"End_Text"; 
<SCRIPT LANGUAGE=JAVASCRIPT> 
<!-- 
document.write('<img src="/cgi-bin/get-img.cgi?'+document.referrer+'"a
+lt="logo" height=103 width=419>') // --> 
</SCRIPT> 
<NOSCRIPT> 
<img src="/cgi-bin/get-img.cgi?noscript" alt="logo" height=103 width=4
+19> 
</NOSCRIPT> 
End_Text
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