Abstract: Our goal is to develop a web server log analysis tool that produces a web site profile and its system resource usage in a way useful to service providers. Understanding the nature of traffic to the web site is crucial in properly designing site support infrastructure, especially for large, busy sites. The main questions we address in this paper are the new access patterns of today's WWW, how to characterize dynamics or evolution of web sites, and how to measure the rate of changes. We propose a set of new metrics to characterize the site dynamics, and we illustrate them with analysis of three different web sites.