1. A system for displaying a selected advertisement on a web page display associated with a list of transactions delivered by a financial institution computer system to a consumer via an Internet-accessible online banking portal to a client machine operated by the consumer and displayed in a web browser of the client machine, the selected advertisement provided from an offer placement system independently of the financial institution computer system, comprising: an offer placement system including a database storing a plurality of potential advertisements and operative to identify a selected advertisement corresponding to a predetermined advertisement selection criterion based on information in a list of currently-displayed transactions received from the client machine, the offer placement system being further operative in response to the identification of a selected advertisement to generate an advertisement return package to the client machine that includes the selected advertisement and advertisement placement information and to transmit the advertisement return package to the client machine; and software installed on the client machine operative for: receiving an account history page from the financial institution computer system comprising a list of transactions in response to a request from the web browser resulting from an event triggered by the consumer; processing the list of transactions to generate a list of currently-displayed transactions; transmitting the list of currently-displayed transactions to the offer placement system; receiving the selected advertisement from the offer placement system; and displaying the selected advertisement in the web browser with the currently-displayed transactions in accordance with predetermined advertisement placement information.