8. A document serving system for creating and/or updating a user vector associated with a user, comprising: a data processing system; a data storage system accessible to the data processing system; and a network interface coupled to a network, said data processing system being configured to: (i) transmit to a user, via the network interface and the network, a document containing a set of terms, including a first term and a second term, wherein a document vector corresponding to the document associates each term included in the set of terms with a term value (vd) such that the first term is associated with a first term value (vd1) and the second term is associated with a second term value (vd2); (ii) receive information identifying two or more actions the user took with respect to the document, the received information being mapped to an action value (a); (iii) determine the action value (a) to which said received information is mapped; (iv) establish a set of term/value pairs in response to receiving the information, wherein the data processing system is configured to establish the set of term/value pairs by determining, for each term included in the set of terms, a value (v) to associate with the term, said value (v) being a function of the determined action value (a) and the term value (vd) associated with said term in the document vector; and (v) store in the data storage system the set of term/value pairs such that the set of term/value pairs is associated with the user.
8. A document serving system for creating and/or updating a user vector associated with a user, comprising: a data processing system; a data storage system accessible to the data processing system; and a network interface coupled to a network, said data processing system being configured to: (i) transmit to a user, via the network interface and the network, a document containing a set of terms, including a first term and a second term, wherein a document vector corresponding to the document associates each term included in the set of terms with a term value (vd) such that the first term is associated with a first term value (vd1) and the second term is associated with a second term value (vd2); (ii) receive information identifying two or more actions the user took with respect to the document, the received information being mapped to an action value (a); (iii) determine the action value (a) to which said received information is mapped; (iv) establish a set of term/value pairs in response to receiving the information, wherein the data processing system is configured to establish the set of term/value pairs by determining, for each term included in the set of terms, a value (v) to associate with the term, said value (v) being a function of the determined action value (a) and the term value (vd) associated with said term in the document vector; and (v) store in the data storage system the set of term/value pairs such that the set of term/value pairs is associated with the user. 9. The document serving system of claim 8 , wherein fee-each term value for a term equals the number of times the term appears in the document.