Tools like Google Analytics allow you to track visits to your Web site. A javascript tracking code snippet placed on every page of your site checks every incoming visitor for information about where they came from and whether they've been to your site before. If you buy pay-per-click media and run Google Analytics, you have probably had the experience of seeing that you purchased X number of clicks, and then got fewer than X visits to your Web site as a result. When you first noticed this, you may have felt that you'd been ripped off — but that's not quite true. In a perfect world, there would be no difference between clicks and visits. Every time someone clicked on your ad, they would successfully get to your site, your page would load correctly, their visit would be correctly attributed to the source that sent them, etc. However, in reality, there are a lot of things that can go wrong along the way, any of which could cause visits to be fewer than clicks:

1. Page load errors. Nobody's Web site loads correctly 100% of the time. Hopefully, your site functions properly the vast majority of the time, but whenever it fails to load for traffic that came from a PPC ad, you get a click without a corresponding visit. These problems may also arise on an individual user level: internet connection failures, clicking the back button before your page loads, clicking your ad but then clicking a different ad before the search results page unloads, accidentally closing the window, etc.

2. Javascript code errors. Google Analytics and many other tracking systems rely on javascript code that runs in your users' browsers, but you may find that as many as 5% of your users do not have javascript enabled. In those cases, or if their javascript fails for some reason, Google Analytics may have some trouble tracking the event (although Google Analytics does have some tools to account for users who don't have javascript).
Note: If you use Google Analytics, you can upgrade to the new asynchronous Google Analytics tracking code. A major advantage to this new code is that you now can put the Analytics tracking code at the top of your page, rather than the bottom; this can decrease breakage that results from javascript and page load errors. It has the added benefit that if the Google Analytics javascript fails for some reason, it will not interfere with any functionality on your page.

3. Attribution errors. Look in your Google Analytics under the medium "referral", and see how many referrals you've gotten from sites like google.com/search, search.yahoo.com, and bing.com. These are visitors who were not correctly attributed to "CPC" or "organic," and got categorized into the default category of generic "referrals" instead. This can occasionally happen with any traffic source.


These types of small errors are just a fact of life in the Web analytics world, but they are not unique to online commerce. In the supermarket business, it's known as "breakage and spoilage". If you ship 10,000 apples from point A, you might be lucky if 9,970 viable apples arrive at point B and make it onto the correct stand in the produce aisle. 1% to 3% "breakage" in Web tracking is typical.

There's a great way to benchmark the amount of "breakage" you typically get on your site. If you have an AdWords account, and you link it to your Google Analytics accounts, you can get side-by-side click and visit data for the same traffic. This gives you a great benchmark for "normal breakage" for your AdWords ads and your Web site.

If you are finding a very dramatic clicks/visits discrepancy (more than 20%), it is most likely the result human error in generating and implement the tracking links. For example, you may be sending traffic to your Web site through a link that is missing Google Analytics tracking parameters, and that traffic is therefore not showing up where you expect it in the Analytics reporting console.  The best way to avoid this problem is through automation. If you have the means, a system that creates and/or tags your tracking links automatically is best. You very rarely hear people complain that their Google Analytics visits stat is way off from their AdWords clicks stat. The reason is that you can set AdWords to automatically append Google Analytics tracking information to your AdWords URLs, so that you never have to edit your URL manually.  Furthermore, AdWords will put all the information you need into one big fancy parameter, "gclid=....", instead of a whole bunch of separate "utm_something=" parameters, which provide much greater opportunity for breakage. A system that integrates automatic tracking link generation with account management, like Clickable, DART Search, or Omniture, gives you the added bonus that all the links you publish out to search engine ad networks will automatically contain the necessary tracking parameters, and you don't have to remember to add or activate them.

There is no perfect solution for Web tracking, whether you're attempting to measure clicks/visits or conversions. Measuring quantities of Web traffic, shipments of apples, or water sprayed from a hose into a jug all suffer the same problem: Most of the stuff goes where it's supposed to, but some of it doesn't. The key to managing and optimizing your online advertising in the face of this challenge is to know whether you have a real problem or just a normal "breakage" discrepancy, and either troubleshooting or just not worrying about it, as the situation dictates.

Ehren Reilly, Clickable SEM Guru

Note: Clickable employees volunteer several hours a week to helping other search marketers succeed. "Clickable Gurus" participate in numerous online search communities to provide straightforward answers to numerous questions, and, each week, one of the gurus posts a search-marketing tip to the Clickable Blog.

One of the most important components of an effective search marketing campaign is conversion tracking