Let's start out by explaining that a persistent cookie (that is, a cookie that remains on your visitor's web browser) is required if you want good quality conversion data or Return on Investment (ROI) on keyword and e-mail campaigns. Some statistics, such as number of users, search keywords, or average time on site don't require a cookie. But sales can often be "latent," that is, that they happen some time after the original visit to the site. The classic example is clicking through on a keyword to a site and then buying the product two days later. A persistent cookie is required to tie the keyword to the sale so you can track true ROI, even though the sale resulted from two distinct visits.

First and Third Party Cookies

Now let's look at two important distinctions. The first distinction is between first party vs. third party cookies. A first party cookie would be set from your own domain. Third party cookies are placed from a separate domain than your own, typically tracking services. For example, a visitor may visit bobsfruitsite.com/apples.htm, but Bob's tracking service uses JavaScript to set a cookie from statsservice.com, that is, a third party.

Cookie Blocking and Deletion

The second important distinction is between cookie blocking vs. cookie deletion. Cookie blocking means that a visitor's web browser automatically refuses to accept third party cookies of any description. They are not accepted. Deletion, on the other hand, is where the browser accepts the cookie but later the user manually removes it. Blocking is comparatively rare because it requires more advanced software. The biggest problem is deletion.

The number one reason cookies are being deleted is because of anti-spyware tools. Although spyware has become a real problem, these tools used to stop it often delete harmless, useful cookies as well as the nasty stuff. Deleting these useful cookies does nothing to prevent true spyware, but most users don't realize that.

Moving away from Third Party Cookies

If you want to get accurate conversion data for your website, you really need to move off third party cookies.

• JavaScript analytics. If you are using a stats or analytics service that uses JavaScript in each page, check with the vendor to see if they support first party cookies. The inexpensive and free ones often don't offer this, so consider switching.
• Logfile analytics. If your analytics are based on logfiles, you have fewer concerns about anti-spyware because any cookies set are certain to be first party. On the other hand, many sites using logfiles actually don't set a cookie to track visitors who return later to make a purchase, so this prevents good ROI data anyway. Talk to your analytics vendor to make sure they can handle a persistent cookie, talk to your web developer about implementing it within your website, and finally talk to your hosting company to make sure they can include the cookie within the logfiles.

Though moving away from third party cookies will substantially help your conversion data, some data will still leak anyway. Some users will delete cookies from inside the web browser so some conversions just won't be seen by your analytics. Nevertheless, since conversion data that gets lost tends to be equal across all campaigns, the best campaigns still rise to the top of the reports make it clear where money should be directed so it impacts the business to the maximum.

"Copyright 2005, Ralph F. Wilson. All rights reserved. Used by permission."