The Webalizer is web log analysis software, which generates web pages of analysis, from access and usage logs. It is one of the most commonly used web server administration tools. It was initiated by Bradford L. Barrett in 1997. Statistics commonly reported by Webalizer include hits, visits, referrers, the visitors' countries, and the amount of data downloaded. These statistics can be viewed graphically and presented by different time frames, such as by day, hour, or month. Website traffic analysis is produced by grouping and aggregating various data items captured by the web server in the form of log files while the website visitor is browsing the website. The Webalizer analyzes web server log files, extracting such items as client's IP addresses, URL paths, processing times, user agents, referrers, etc. and grouping them in order to produce HTML reports. Web servers log HTTP traffic using different file formats. Common file formats are Common Log Format (CLF), the Apache Custom Log Format, and Extended Log File Format. An example of a CLF log line is shown below. 192.168.1.20 - - [26/Dec/2006:03:09:16 -0500] "GET HTTP/ 1.1" 200 1774 Apache Custom Log Format can be customized to log most HTTP parameters, including request processing time and the size of the request itself. The format of a custom log is controlled by the format line. A typical Apache log format configuration is shown below. LogFormat "%a %l "%u" %t %m "%U" "%q" %p %>s %b %D "%{Referer}i" "%{User-Agent}i"" my_custom_log CustomLog logs/access_log my_custom_log Microsoft's Internet Information Services (IIS) web server logs HTTP traffic in W3C Extended Log File Format. Similarly to Apache Custom Log format, IIS logs may be configured to capture such extended parameters as request processing time. W3C extended logs may be recognized by the presence of one or more format lines, such as the one shown below. #Fields: date time s-ip cs-method cs-uri-stem cs-uri-query s-port cs-username c-ip cs(User-Agent) cs(Referer) sc-status sc-bytes cs-bytes time-taken The Webalizer can process CLF, Apache and W3C Extended log files, as well as HTTP proxy log files produced by Squid servers.