This course discusses basic information retrieval models, evaluation methods, state of art of search engines and new trends in web search. Topics covered include basic IR models, indexing, query operation, evaluation, categorization and clustering, web search, link analysis, web crawling, web mining, etc. After completing this course, students will have acquired the core techniques in building text retrieval systems, hands-on experience in building the core parts of a web-based search engine, and knowledge of IR applications on the world wide web.