Abstract: Content is selected for display at a client computer communicating over a computer network by determining a relevance score for content of a document at a server computer for delivery to a requesting client computer, determining at least one valuation for the content from each of two or more supplemental content sources, generating a productivity score for each of the supplemental content sources in accordance with the corresponding content valuation for the supplemental content source, selecting the supplemental content source having the greatest productivity score, and serving the document and supplemental content from the selected supplemental content source for delivery to the requesting client computer.

Abstract: A system for use on computer servers on a network serving client computers for selecting an advertisement to be presented among a plurality of possible advertisement candidates based on key words. When a client computer requests a document from a server on the network, the system considers words contained within the document and compares them to a set of key words for each possible advertisement of a plurality of possible advertisements. The system selects an advertisement to be presented with the information where a key word associated with the advertisement matches one or more words in the document. If more than one advertisement qualifies, the system considers a price value of each advertisement and a relevance score for each word, which is a function of proximity to the start of the document, to determine which advertisement will be presented.