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. 15. The manufacture of claim 12 , wherein the instructions further comprise instructions that cause the one or more processing devices to: apply an expectation maximization algorithm to the documents in the document set that were not selected by the user for viewing to generate negative labels for certain ones of the non-selected documents, and positive labels for the rest of the non-selected documents; and wherein, to generate at least one negative word vector, the instructions include instructions that cause the one or more processing devices to generate at least one negative word vector using words contained in at least a segment of the documents for which the expectation maximization algorithm generates negative labels.