Determining which Sales/Conversions Come from which Advertising Method

There are two methods:

The best way is to track user sessions with cookies. If you create a user session (by setting a cookie on the user's computer) when someone visits your site, then you can count how many user sessions resulted in a conversion (i.e., the user made a purchase). You can then analyse the referral source for each of your user sessions (likely from the referral URL in your server log) and count how many conversions came from each advertising method. This last step is made much easier if you use tracking URLs.

If you're not using cookies, analyse the IP address of each visitor. Your Web server records the IP address of each visitor to your site. However, relying on unique IP addresses is imperfect for a number of reasons. Some Internet service providers and organisations use dynamic IP addressing, where an IP address is assigned dynamically when a user logs into a host system. This can be problematic because the same user may be assigned different IP addresses each time he or she visits, and therefore you won't be able to tell it was actually that same user.

Others, pass information requests through a proxy server, causing all requests to appear to come from a small number of IP addresses (those of the proxy servers, not the users). Third party tracking software makes IP tracking easier, but has other drawbacks that may preclude you from getting the most accurate records.* Read more about this in the previous section.

* At time of publication.