1. A method for delivering a targeted advertisement, comprising the steps of: generating a first identifier corresponding to a first computer; sending the first identifier to the first computer; receiving a second identifier corresponding to a consumer from the first computer; associating the first identifier with the consumer by linking the first identifier to the second identifier corresponding to the consumer; classifying the consumer by assigning to the consumer a purchase behavior classification based on at least one selected purchase behavior criterion and an observed offline purchase history corresponding to the second identifier; selecting a targeted advertisement to be delivered to the consumer, based on the purchase behavior classification assigned to the consumer; receiving from the first computer the first identifier corresponding to the first computer and associated with the observed offline purchase history of the consumer, the offline purchase history including information of an offline purchase of a consumer collected when the offline purchase transpired; electronically delivering the targeted advertisement to the consumer at the first computer in response to receiving the first identifier from the first computer; reclassifying the consumer by assigning to the consumer an updated purchase behavior classification based on at least one selected purchase behavior criterion and an updated observed offline purchase history corresponding to the second identifier; and reselecting the targeted advertisement to be delivered, based on the updated purchase behavior classification assigned to the consumer.