10. A processor-implemented method, comprising: receiving a request for an initial document in a plurality of documents from a user; identifying documents in the plurality of documents that are related to the initial document, comprising: assigning scores to other documents in the plurality of documents, including — determining, for each other document in the plurality of documents, if a the document has an associated compressed document surrogate, when the document has an associated compressed document surrogate, assigning a score to the document based on occurrences of at least one term included in the initial document in the associated compressed document surrogate, wherein a score of S D assigned to a document D in the plurality of documents is determined by crediting the document D, for each term T in the initial document which occurs in the compressed document surrogate associated with document D, with an amount proportional to Robertson's term frequency TF TD and to IDF T where 
 TF TD =N TD/ ( N TD +K 1 +K 2 *( L D /L ) )),and N TD is the number of times the term T occurs in compressed document surrogate D, L D is the length of compressed document surrogate D, L 0 is the average length of a document in the plurality of documents, K 1 and K 2 are constants, and 
 IDF T =log ((N+K 3 /log (N+K 4 ), and N is the number of documents in the plurality of documents, N T is the number of documents containing the term T in the plurality of documents, and K 3 and K 4 are constants, selecting a set of documents from the plurality of documents based on the assigned scores; and presenting information identifying the set of documents to the user.
10. A processor-implemented method, comprising: receiving a request for an initial document in a plurality of documents from a user; identifying documents in the plurality of documents that are related to the initial document, comprising: assigning scores to other documents in the plurality of documents, including — determining, for each other document in the plurality of documents, if a the document has an associated compressed document surrogate, when the document has an associated compressed document surrogate, assigning a score to the document based on occurrences of at least one term included in the initial document in the associated compressed document surrogate, wherein a score of S D assigned to a document D in the plurality of documents is determined by crediting the document D, for each term T in the initial document which occurs in the compressed document surrogate associated with document D, with an amount proportional to Robertson's term frequency TF TD and to IDF T where 
 TF TD =N TD/ ( N TD +K 1 +K 2 *( L D /L ) )),and N TD is the number of times the term T occurs in compressed document surrogate D, L D is the length of compressed document surrogate D, L 0 is the average length of a document in the plurality of documents, K 1 and K 2 are constants, and 
 IDF T =log ((N+K 3 /log (N+K 4 ), and N is the number of documents in the plurality of documents, N T is the number of documents containing the term T in the plurality of documents, and K 3 and K 4 are constants, selecting a set of documents from the plurality of documents based on the assigned scores; and presenting information identifying the set of documents to the user. 13. The method of claim 10 , wherein the documents are Web pages, and the collection of documents comprises Web pages available from a Web site.