Every time your Web server receives a request from a visitor and displays a Web page for that visitor, it creates an entry for the request in a log file on the Web server. The log file records all the activity your Web site experiences. The server captures a lot of information in this file that you can then use to get a better idea of how your Web site is being used and operated by visitors and customers.
A log file is just a text file stored on your Web server that receives a new entry whenever your Web server has to fulfill a request from a Web browser. Sometimes, the log file is called the access log file (see Figure 5-1). Other times, the Web server breaks the log file into different files, for example, an error log, a request log, and a referrer log.
Your log files tell you a lot about your Web site:
Your Web site measures a hit whenever a piece of your Web site, whether it's a Web page or a graphics file or another object, is sent over the Internet ...