in 1997 by Jakob Nielsen.

Zipf Distribution (power law) of Website Popularity (Alertbox Sidebar): "Much available data suggests that Web use follows a Zipf distribution. The figure shows the distribution of incoming page requests to www.sun.com during a one-month period last year. Each datapoint represents one page, with the x-axis showing pages sorted according to popularity: the first page is the most popular one (the home page), the second page is the one that received second-most requests that month, and so on until we reach page number 10,000 which was only requested a single time that month. The heavy line shows the actual empirical data from the log files and the thin red line shows a Zipf curve that seems to fit the data quite well except for the low end. The deviation at the low end is due to a variety of factors, including the fact that the site is not old enough yet to have enough accumulated pages of low-frequency interest."