Fabulous mod !
I've extended this a bit to make the referrer a selectable option
add the following in /config.php after the # Defined Titles area
Code:
#
# Defined Referrers
#
$name_referrers = array("Search Engine","Magazine Ad","Newspaper Ad","Word of Mouth","Other");
$smarty->assign("name_referrers",$name_referrers);
In main/register.tpl use the following:
Code:
<tr valign=middle>
<td align=right>{$lng.lbl_referer}</td>
<td></td>
<td nowrap>
<select name=referred>
{section name=referred loop=$name_referrers}
<option {if $userinfo.referred eq $name_referrers[referred]}selected{/if}>{$name_referrers[referred]}</option>
{/section}
</select>
</td>
</tr>
Also for reference, if you're having trouble seeing the original mod correctly, make sure you add lbl_referrer to the languages table
