1. A non-transitory computer-readable medium embodying a program executable in a computing device, the program comprising: code that sends a network page to a client, the network page including at least one component for requesting that at least one product be added to a shopping list; code that adds the at least one product to the shopping list in response to a request from the client; code that encodes a preliminary display region for rendering in the client as a layer superimposed on the network page when at least one of the at least one product is currently in the shopping list, and the preliminary display region is configured to obtain a user confirmation whether to proceed with adding the at least one product to the shopping list; code that encodes a display region for rendering in the client as a layer superimposed on the network page and obscuring a portion of the network page, a remaining portion of the network page being dimmed, the display region including a confirmation that the at least one product has been added to the shopping list, the display region including at least one undo component for requesting that a last modification to the shopping list be reversed; and code that configures a forward browser control and a back browser control to navigate serially between the network page and a plurality of instances of modified content rendered within the display region, at least some of the instances of modified content corresponding to a response to a respective request to modify the shopping list.