Description:This book constitutes the thoroughly refereed post-proceedings of the 6th International Workshop on Mining Web Data, WEBKDD 2004, held in Seattle, WA, USA in August 2004 in conjunction with the 10th ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, KDD 2004. The 11 revised full papers presented together with a detailed preface went through two rounds of reviewing and improvement and were carfully selected for inclusion in the book. The extended papers are subdivided into 4 general groups: Web usage analysis and user modeling, Web personalization and recommender systems, search personalization, and semantic Web mining. The latter contains also papers from the joint KDD workshop on Mining for and from the Semantic Web, MSW 2004.