What are the most popular Web analytics tools?

Google Analytics (www.google.com/analytics/) is in a class by itself. It offers substantially more functionality than the other basic tools, but is free.

Unlike tools such as Webalyzer or AWStats, you need to install Google Analytics on your site, which involves pasting a chuck of HTML (provided by Google) into every page. This obviously requires a bit of HTML know-how, but if you know what you're doing, shouldn't require too much effort. Depending on the size of your site and how it's set up, installing the Google Analytics code might take anywhere from a couple of minutes to a few hours. Once the code is added, Google displays your statistics in a custom reporting interface that you can view online.

In addition to the reports offered by tools like Webalizer or AWStats, Google allows you to find out how often visitors come to your site, tracks visitor conversion across a series of pages, compares the behavior of different types of visitors (such as new versus returning, or those from different referring sites), and much more. A selectable date range allows you to analyze any given time period, instead of being limited to a monthly view (as you are with AWStats and Webalizer). Google has a nifty feature that allows you to look at a rendered version of the site and see the percentage of people that clicked each link on a given page.