The task of clustering Web sessions is to group Web sessions based on similarity and consists of maximizing the intra-

group similarity while minimizing the inter-group similarity．

The first and foremost question needed to be considered in clustering

W b sessions is how to measure the similarity between Web

sessions．However．there are many shortcomings in traditiona1

measurements．This paper introduces a new method for measuring

similarities between Web pages that takes into account not only the

URL but also the viewing time of the visited web page．Yhen we

give a new method to measure the similarity of Web sessions using

sequence alignment and the similarity of W eb page access in detail

Experiments have proved that our method is valid and e币cient．