A system and method for monitoring and analyzing Internet traffic is provided that is efficient, completely automated, and fast enough to handle the busiest websites on the Internet, processing data many times faster than existing systems. The system and method of the present invention processes data by reading log files produced by web servers, or by interfacing with the web server in real time, processing the data as it occurs. The system and method of the present invention can be applied to one website or thousands of websites, whether they reside on one server or multiple servers. The multi-site and sub-reporting capabilities of the system and method of the present invention makes it applicable to servers containing thousands of websites and entire on-line communities. In one embodiment, the system and method of the present invention includes e-commerce analysis and reporting functionality, in which data from standard traffic logs is received and merged with data from e-commerce systems. The system and method of the present invention can produce reports showing detailed "return on investment" information, including identifying which banner ads, referrals, domains, etc. are producing specific dollars.