1. A method for mining websites, comprising: obtaining web usage data for users of a website, wherein the website is a hierarchical structure of webpages, and wherein each webpage comprises content categorized into at least two granular levels of the hierarchical structure; constructing a plurality of hierarchical user session data structures, wherein each hierarchical user session data structure comprises the web usage data from a user session that is organized based on the hierarchical structure of the website; normalizing each of the hierarchical user session data structures by dividing the number of webpages in each level of the hierarchical structure of webpages viewed during each user session by a total number of webpages in the website viewed during each user session; comparing metrics of the plurality of normalized hierarchical user session data structures to determine closeness between the plurality of hierarchical user session data structures; and clustering two or more of the plurality of normalized hierarchical user session data structures into groups based on ranking the determined closeness.