The arrival of World Wide Web (WWW) has brought in huge amount of data which keeps growing dynamically. This necessitates the requirement of new tools and processes that can intelligently and automatically transform data into useful information and knowledge, especially such knowledge, which is subtle and hidden in the data. Knowledge Discovery is such a process. Knowledge discovery takes the form of Web mining for extracting useful and meaningful information from the Web. Web Mining revolves around automatic discovery and extraction of useful information from World Wide Web documents and services. Web usage mining is one of the web mining techniques which involves the task of discovering the activities of the user while they are browsing or navigating through the web. The navigation preferences of the visitors can be analyzed to enhance the quality of electronic commerce services, to personalize the web portion, to improve the web structure and server performances. This book aims at discovering interesting patterns from web log data by means of applying novel algorithms and presenting the results.