<a href="http://NextTag.com">NextTag.com</a> is a service that aggregates product info from different vendors and offers comparison shopping. Essentially, vendors have to work to ensure that they offer the lowest prices for a product so that when a consumer compares prices among the same product types, their products get clicked.

When a consumer clicks on a product, they&apos;re taken to the vendors site and if they buy a product, NextTag gets a cut. In order to determine whether they came from a NextTag, a vendor needs to include the following snippet into the final page of the order process:

<code>
<script type="text/javascript">

    /* NexTag ROI Optimizer Data */
    var id = &apos;1234567&apos;; // Merchant ID
    var rev = &apos;12.99&apos;; // Total amt of the purchase

</script>
<script type="text/javascript" src="https://imgsrv.nextag.com/imagefiles/includes/roitrack.js"></script>	
</code>

This snippet somehow allows NextTag to differentiate between normal orders and order explicitly referred by NextTag. For example, if you receive 10 orders today and 3 were referred by NextTag, the code snippet somehow knows this.

I want to do something like this but can&apos;t for the life of me figure out how they did it. I checked my cookies and there are no NextTag cookies set at all (sub-domain either). JellyFish.com, Google Adwords, & Overture all do something similar.

JellyFish:

<code>
<!-- Begin Jellyfish Tracking Pixel Code -->
<script type=&apos;text/javascript&apos;>
var jf_merchant_id = &apos;YOUR_CUSTOM_MERCHANT_ID&apos;;
var jf_merchant_order_num = &apos;ORDER_NUMBER&apos;;
var jf_purchased_items = new Array();
// adding cart items
FOR EACH PURCHASED ITEM...
// add cart item
var jf_item = new Object();
jf_item.mpi = &apos;ITEM_PRODUCT_ID&apos;;
jf_item.price = &apos;ITEM_PRICE&apos;;
jf_item.quantity = ITEM_QUANTITY;
jf_purchased_items.push(jf_item);
NEXT PURCHASED ITEM

</script>
<script type=&apos;text/javascript&apos;
src=&apos;https://www.jellyfish.com/javascripts/1x1tracking.js&apos;>
</script>
<!-- End Jellyfish Tracking Pixel Code -->
</code>

Can anyone shed some insight on how this is done?