what he means is that the code amazon provides you actually contains two elements...
the first element is your affiliate link....the second element is a tracking pixel.
example....this is the first part, the link itself
<a href="http://www.amazon.com/b?%5Fencoding=UTF8&site-redirect=&node=1000&tag=xxxx-20&linkCode=ur2&camp=1789&creative=9325">100 hot books</a>
This is the second part, the tracking pixel. This is what allows them to track impressions.
<img src="http://www.assoc-amazon.com/e/ir?t=xxxx-20&l=ur2&o=1" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />
What I would be really interested in knowing though is the original question...if my affiliate link goes to a single item or category...do I actually get credit for any other purchases the person makes? Or just the item in the link? As far as I could tell...visiting the affiliate link didn't ACTUALLY give me an affiliate cookie...it may have been encoded into the session cookie somehow...but it looked to me like it was the same cookie I would have gotten by just plain old visiting amazon.com
If that were the case...how do you guys effectively Stuff amazoN?