WWW continues to grow at an overwhelming rate in both the sheer volume of traffic and the size & complexity of Web sites. Therefore, it becomes more and more necessary, but difficult to get useful information from Web data, in order to understand and better serve the needs of Web-based applications. As a result, the Web usage mining has become a hot research topic, which combines two of the prominent research areas comprising the data mining and the World Wide Web.The book gives all the details of two contributions from this research work those are preprocessing of web log data and clustering of web users based on thier interest. ART1 NN algorithm is used for clustering and finally it has been proved that ART1 performs better than traditional k-means and SOM clustering algorithms.