Web Analytics Tutorial

Lesson 1 – What is Web Analytics?

Basic Units of Measure

When generating and discussing web metrics, there are several units that are commonly referred to. It is important to know the distinction between these so that you know what you are looking at. One of the most common metrics is ‘hits.’ You often hear people saying “we had 10,000 hits this week on our website.” Unfortunately, statements like that are not well defined. This kind of information usually comes from a ‘hit counter’ placed on the home page of the site. In this case, what this person really means is “we had 10,000 hits on our home page last week.” Hit counters serve their purpose, but only provide basic information. Web analytics allows you to go much deeper, without losing this basic information.

Hits and impressions

In most web analytics discussions a ‘hit’ is defined as a single request for any item on your website. This can include images, animations, audio, video, downloads, PDF or Word documents or anything else that you allow visitors to access. When a web browser loads a page, it also loads all the components referenced by that page. This means that it requests all the images (often including ‘roll over’ images for mouse effects) and, perhaps, stylesheets, JavaScript files or other external references. A single page load can result in many ‘hits.’

Quickly, pull up the home page of your site and see if you can figure out how many ‘hits’ you generated by doing that: count all the graphics that it loads. If you are familiar with HTML, look at the source and see if there are external stylesheets, script files, or roll-over images that are loaded invisibly. You may be surprised at the number of items required just to build your home page.

The term ‘impression’ has been adopted into web analytics lingo from traditional advertising. In advertising, a count of impressions is the number of times an advertisement has been seen or heard. This is usually very hard to count (in newspapers, radio or television) and is often estimated. With websites, we have logs to tell us the number of hits the server has registered for the ad. When requests for a particular item, such as a page or advertisement are counted, these hits can nominally indicate how many times the item was seen and are therefore sometimes counted as impressions.

So if a single request to the home page can generate many hits in your logs, what value is a hit count? Mainly it is useful for managing or monitoring the load on your server. Each hit represents a single network request. So a large number of hits corresponds to many processes that your server has to deal with and more traffic over your network connection. It is also a general indication of traffic volume and can, therefore, be used to view growth of your website.

It can be indicative of the user experience. If a single visit to your home page generates 75 hits, that means the new visitor has to wait through loading 75 items before she gets the full experience. Most browsers will only load four or five items at a time, so loading the home page will take a while. It might be a good idea to rethink the design of that site to reduce the number of items on the pages so they load faster. (Browsers do actually cache items; the effect of this on your statistics are discussed in detail in Appendix B.)

Page views

Figure 1. The Overview Content Report includes summaries of different types of hits.

Page hits are a much more useful metric than hits for analyzing user experience. Web sites are organized into pages, and users (and designers) think of them in pages, so counting page hits makes more sense. Now that you have loaded your home page, wander around your site a bit. Keep track of the number of times a new page loads. This is the number of page hits your visit is registering. The more time you spend on the site, exploring, the more page hits you register. So page hits represents the navigational experience of the visitor.

There is one situation in which page hits do not correlate directly to the user experience. If your site uses frames, the frameset page and all the frames that load to make the ‘visible page’ are each counted as a single page hit. So if your ‘home page’ actually is a frameset with three frames, it will register four page hits, not one (what the user is experiencing) for that initial load. If the visitor then clicks on a link that only changes one frame, that will register as a single page hit. If you have built your site so that each click loads a whole new frameset, then you will get multiple page hits for each click the visitor performs. If you understand the design of your site, however, you can easily adjust the page hits count to reflect these aspects.

Graphics hits

Other types of hits are important too. “Graphics Hits,” as shown in Figure 1, are the number of requests for images, animations or other graphics. Graphics are often larger than the content of a page and take up a good portion of bandwidth as well as requiring the visitor to wait while the page loads. Looking at Figure 1, you can see there were 19,493 Graphics Hits. If the number of graphics hits for your site is significantly larger than that of page hits, then there are probably a lot of graphics on some or all of your pages. You might consider redesigning the site to make it load faster.

Downloads

Finally, Summary counts “Downloads.” This can be programs, archives, zip files, or PDF documents that users download from your site. If you distribute software or documents from the site, it is helpful to have a quick count of the number of downloads in each period.

Figure 2. The Monthly Report shows several metrics for each month.

Errors

One of the great features of Summary is that these metrics are counted in the context of many of the reports. So, for example, every period in the time reports contains columns of Hits and Pages, as well as other useful information. In Figure 2, you see a Summary Monthly Report. Notice the columns of Errors, Bytes, Unique Hosts and Visits. Errors are simply a count of the number of requests for items that did not complete – either because they were not there or could not be produced. It is a quick measurement of your site’s diagnostics.

Bytes

There are other factors that can affect the byte-to-page-hit value that make this ratio only useful in some situations. If you have any downloads on your site, this will likely increase the byte count significantly. On the other hand, as discussed in Appendix B – Technical Details of Metric Accuracy, caches can make the byte counts significantly lower than if all graphics were loaded. When assessing the byte-to-page-hits ratio, you may want to consider the environment as well. For example, if these statistics are for an intranet, where users have a lot of available bandwidth, you may be perfectly comfortable with a 100KB-per-page average, where you would not be when your visitors were using 56k dial-up Internet connections. Nonetheless, the byte count does accurately reflect the amount of data requested from your server.