A. Given B. hyperlinks C. repository D. immediate E. query F. relevance G. disguised H. pervasive I. indexing J. yield K. submitted L. retrieves M. associated N. derives O. interactive P. medium The first major impact of the Web on search is related to the characteristics of the document collection itself. The Web collection is composed of documents (or pages) distributed over millions of sites and connected through 1 , i.e., links that associate a piece of text of a page with other Web pages. The inherent distributed nature of the Web collection requires collecting all documents and storing copies of them in a central repository, prior to 2 . This new phase in the IR process, introduced by the Web, is called crawling. The second major impact of the Web on search is related to the size of the collec­tion and the volume of user queries 3 on a daily basis. 4 that the Web grew larger and faster than any previous known text collection, the search engines have now to handle a volume of text that far exceeds 20 billion pages. The combination of a very large text collection with a very high 5 traffic has pushed the performance and scalability of search engines to limits that largely exceed those of any previous IR system. That is, performance and scalability have become critical characteristics of the IR system, much more than they used to be prior to the Web. The third major impact of the Web on search is also related to the vast size of the document collection. In a very large collection, predicting 6 is much harder than before. Basically, any query 7 a large number of documents that match its terms, which means that there are many noisy (irrelevant) documents in the set of retrieved documents. This problem first showed up in the early Web search engines and became more severe as the Web grew. Two other major impacts of the Web on search derive from the fact that the Web is not just a(n) 8 of documents and data, but also a(n) 9 to do business. One 10 implication is that the search problem has been extended beyond the seek­ing of text information to also encompass other user needs such as the price of a book, the phone number of a hotel, the link for downloading software. Providing effective answers to these types of information needs frequently requires identifying structured data 11 with the object of interest such as price, location, or descriptions of some of its key characteristics. The fifth and final impact of the Web on search 12 from Web advertising and other economic incentives. The continued success of the Web as a(n) 13 media for the masses created incentives for its economic exploration in the form of, for instance, advertising and electronic commerce. These incentives led also to the abusive availability of commercial information 14 in the form of purely informational content, which is usually referred to as Web spam. The increasingly 15 presence of spam on the Web has made the quest for relevance even more difficult than before.