Web Analytics Tutorial

Lesson 1 – What is Web Analytics?

IN THIS LESSON

Introduction

Basic Units of Measure

Bytes

Advanced Units of Measure

Users

Unique hosts

Visits or sessions

Visit tracking with cookies

Further Study

Advanced Units of Measure

Users

Figure 3. The User Report shows
which users are most active.

So far we have discussed metrics that are helpful in relating content to user experience, but you are probably wondering now just how many users experienced your content. The most accurate way of counting users is to require them to login. If you use your web server’s authentication system, then each user’s request will be associated with his username. By counting unique usernames you can know the number of unique users over the course of a period. The Summary User Report (Figure 3) can also tell you which users are most active on your site.

Figure 4. The Monthly Report shows several metrics for each month.

Unique hosts

Unfortunately, most websites do not require login. Because of the way the HTTP protocol was designed, there is no connection between requests by the same user to your server. So without requiring authentication, visitors and their visits have to be estimated.

In the past an estimate of unique visitors could be found by looking at the Unique Hosts. Each request that a visitor makes to the site (whether for a page or for the graphics and other referenced files from that page) is associated with a host address (or IP number). When the Internet first started, each computer connected to it had its own host address, so a count of unique hosts was usually a good indicator of the number of unique visitors you had in a given period.

Unfortunately this is no longer true. The majority of Internet users connect through dial-up services of some kind. In order to preserve IP numbers (there are a limited number available right now), the dial-up providers will assign each user a number when he connects and then reuse the number when he is done with it. So a dial-up service may have 100 IP numbers that they select from and use to serve 2000 users. This gets even more complicated with caches and proxies that many providers now use to improve performance (this is covered in more detail in Appendix B).

There is still value to counting unique hosts. A comparative value of unique hosts as a trend over time can be indicative of the reach or breadth of coverage that your website is getting. If you increase the number of unique hosts per month in a six month period, then you probably reaching a broader group of visitors.

Visits or sessions

In addition to counting the number of unique visitors you have had, you often want to know how many visits you have had. A given user may visit the site three distinct times in the course of a month. This would count as three visits. Summary uses some complicated heuristics to determine all the requests in a given visits. The nature of the web makes it impossible to know exactly what requests belong to each individual visit, but Summary uses advanced statistical analysis methods to estimate this. The Visit count can therefore be used as an estimate of the number of visits that occurred in a period. For example, in Figure 4, the first month shows 3,854 visits.

Another common term for visits is ‘sessions.’ This is because a visit is often defined as a series of consecutive requests from a given user bounded by inactivity. So if a user makes 100 requests, then does not make any for 45 minutes, then 75 more, it is assumed those were two separate ‘sessions’ or ‘visits’ to your site.

Visit tracking with cookies

Cookies One of the most common techniques for improving visit metrics and request data in general is to configure your web server to send out a ‘session cookie.’ A cookie is a small bit of information that your site can have visitors store with their browsers. Whenever they request a page, the browser sends the cookie back to your server. Cookies can be given an expiration date if you want them to last for a while. A ‘session cookie’ has no expiration date set so the browser deletes it as soon as the session completes (usually when the user closes the browser). Session cookies are therefore unique to each visit. While a given browser in a given visit may still cache some of the requests, two different visitors accessing your site through a web cache or proxy server will have to make distinct requests.

With a properly configured server and properly configured analysis software, you can even use these cookies to help the software figure out what requests comprise each visit. Summary SP will allow you to configure it to track visit cookies in your logs. In order to make this most effective you should configure your web server to log outgoing and incoming cookies so that you can correlate the first request with subsequent requests in a visit.

While this is much more accurate than the heuristic approach, especially when dealing with proxy sharing, it does not provide a perfect solution. Some users will adamantly refuse to accept cookies from your sites. Other user agents (like robots or spiders) never accept cookies. Finally, some firewalls and proxies will strip cookies from requests completely. If you require users to accept cookies, you may be blocking a large number of potential visitors. If you do not, then you are back to having some visits without cookie data and the previously mentioned issues all return.