19. A method of enabling advertisers to list an advertisement for publication through a multi-node hierarchical content-based system, the method implemented by a server system and comprising: sending, through a communication interface, a multi-level representation of at least a portion of the hierarchy of content nodes to a plurality of advertiser user systems to facilitate selection of one or more of the nodes, the hierarchy of content nodes providing a categorization of information and each content node being associated with one or more web pages; receiving, through a communication interface, advertisement listing information from a plurality of advertiser user systems connecting to the Internet advertising system over the Internet, the advertisement listing information comprising an advertisement title and URL, a selection of one or more nodes with which the advertisement listing information is to be associated, and a bid amount for each node selected; storing the advertisement listings in a database; and publishing, using one or more data processors, web page content and advertisement listings to an end user requesting a particular page associated with a node within the multi-node hierarchical system, the published information including content associated with the node associated with the page requested and advertisements associated with that particular node.
19. A method of enabling advertisers to list an advertisement for publication through a multi-node hierarchical content-based system, the method implemented by a server system and comprising: sending, through a communication interface, a multi-level representation of at least a portion of the hierarchy of content nodes to a plurality of advertiser user systems to facilitate selection of one or more of the nodes, the hierarchy of content nodes providing a categorization of information and each content node being associated with one or more web pages; receiving, through a communication interface, advertisement listing information from a plurality of advertiser user systems connecting to the Internet advertising system over the Internet, the advertisement listing information comprising an advertisement title and URL, a selection of one or more nodes with which the advertisement listing information is to be associated, and a bid amount for each node selected; storing the advertisement listings in a database; and publishing, using one or more data processors, web page content and advertisement listings to an end user requesting a particular page associated with a node within the multi-node hierarchical system, the published information including content associated with the node associated with the page requested and advertisements associated with that particular node. 27. The method of claim 19 further comprising the steps of: storing a set of rules applicable to the Internet advertising system; determining whether a proposed advertisement listing complies with the set of rules; and refusing a proposed advertisement listing that fails to comply with the set of rules.