To track the customers and save their information, Zencart utilizes cookie and session. You will see Zencart usually automatically appends a random string to the end of your links on the very first page of your visit to your site.
For example, if you are not on your website now and you open it in a new window, you will the links look like this:
If set up correctly, when you click on one of those links, on the next page load you will see all link appear without the zenid string. Also, if set up correctly, those links with zenid appended to them should never be displayed to search engine (check your settings under Admin-Configuration: Prevent spider sessions should be set to True).
However, that setting does not prevent zenid appears in some of your reports you get from Google Analytics however (assume that you use G.A). For example, if you check your “site overlay” you might be in for a surprise, most of your links might have a 0% click rate, and you know this cannot be true. If you look closer, however, you will discover that the zenid is in those links. This perhaps can be explained by 2 reasons:
1. Although zenid is never shown to search engine spiders, it does get shown to normal visitors for the reason given above.
2. In any case, the links with zenid are recorded by Google Analytics and since each customer is assigned a different zenid per visit session, the links then appear to be different links
(from Google Analytics point of view, the 2 links above are totally different)
The cure to this is surprisingly easy. Google knows that some parameter(s) in your links should be ignored, and it allows you to do so by the Exclude query parameters setting which only takes a few minutes to do. For all Zencart store, zenid the one you MUST exclude, and depend on the customization you have done on your store you may decide to exclude some other params as well.
I hope this info will help you to use G.A more effectively in the future.