How to add referral box into site

You might have wondered how to put a box on your site where your visitors can just put a referral ID of an affiliate so the affiliate will be credited even though the visitor did not came to your site via a banner or an affiliate link.

Just put this code into any site with clicks tracking code:

<form action="" method="GET">
Refer: <input type="text" name="a_aid"/> <input type="submit" value="Apply"/>

This assumes that URL parameter "Affiliate ID / referrer ID" is the default a_aid. If you have different parameter, then change it.