12. An article of manufacture comprising a computer-readable storage device storing computer-readable instructions which, when executed, cause one or more processing devices to perform the following: access information indicating which documents in a set of documents were selected by a user for viewing and which documents in the set of documents were not selected by the user for viewing; generate at least one positive word vector using words contained in at least a segment of at least one of the documents that was selected by the user for viewing; generate at least one negative word vector using words contained in at least a segment of at least one of the documents that was not selected by the user for viewing; generate document word vectors for at least some of the documents that were selected by the user for viewing; perform, using at least one processor, a vector space relationship analysis of the positive word vector, the negative word vector, and the document word vectors; establish, using at least one processor, a document rank order of the documents selected by the user for viewing based on the performed vector space relationship analysis; classify the documents selected by the user for viewing in predetermined categories; rank the predetermined categories based on the document rank order; send the ranked categories to an ad server; and receive advertisements associated with the ranked categories from the ad server in a selected context.
12. An article of manufacture comprising a computer-readable storage device storing computer-readable instructions which, when executed, cause one or more processing devices to perform the following: access information indicating which documents in a set of documents were selected by a user for viewing and which documents in the set of documents were not selected by the user for viewing; generate at least one positive word vector using words contained in at least a segment of at least one of the documents that was selected by the user for viewing; generate at least one negative word vector using words contained in at least a segment of at least one of the documents that was not selected by the user for viewing; generate document word vectors for at least some of the documents that were selected by the user for viewing; perform, using at least one processor, a vector space relationship analysis of the positive word vector, the negative word vector, and the document word vectors; establish, using at least one processor, a document rank order of the documents selected by the user for viewing based on the performed vector space relationship analysis; classify the documents selected by the user for viewing in predetermined categories; rank the predetermined categories based on the document rank order; send the ranked categories to an ad server; and receive advertisements associated with the ranked categories from the ad server in a selected context. 16. The manufacture of claim 12 , wherein the instructions further comprise instructions that cause the one or more processing devices to: access a document dictionary that contains dictionary words; and wherein, to generate document word vectors, the instructions include instructions that cause the one or more processing devices to, for each document in the group of documents, store a count of the number of occurrences of each dictionary word found in the document.