Your server logs record every URL that was entered (or clicked on) to get to your site. Whenever people order, you can go to your server logs and match time they ordered to time that hits to your sales page were received using unique code. This will help you to determine which ad brought in sale.

If you do not have access to your server logs or you do not know how to use them, there are many free and inexpensive stat tracking solutions available on internet that are easy to understand and implement. Here is one that we highly recommend using: Sitegauge

How will you determine which ads were effective? In offline world, advertising is measured in response rate. This means how many people responded to your ad (responded could mean clickthrus, sales or even subscribers to your ezine). You have to decide which of possible responses is valuable to you. Are you trying to get more traffic, more sales or simply capture email addresses so you can follow up at a later date?

Since we are talking about sales in this article, you have to determine how many visitors it takes before you get a sale. If an ad brought in 100 visitors and you had 4 sales, then you have a 25% response rate. That is quite amazing. You would then want to keep running ad in ezine that brought you that response rate until you see rate start to drop dramatically.

What you have just learned is key to cost effective advertising. Advertising, when performed efficiently is like an exact science instead of a guessing game. This is scientific advertising at it's best!

P.S. An even simpler (albeit not free) way of tracking ads is to purchase affiliate software and use it to track your ads by manually assigning each ad a unique affiliate id. This is very simple to do and can be set up quite easily.