1. An apparatus for presenting one of products and services while providing an a user interactive informational service on a network, comprising: an advertising selector for determining, for each of a plurality of users, a corresponding advertising presentation, from a plurality of advertising presentations, to present to the user at a corresponding node of the network, wherein each presentation (P) of at least some presentations of said corresponding advertising presentations is unrequested , and is used for presenting information about at least one of a product and a service; wherein the advertising selector communicates with each node for the plurality of users through the network; a service providing computational system for providing a first of the users with a requested corresponding instance of the informational service, wherein the instance includes a plurality of user interactions by the first user , via each user interaction providing data for a corresponding different transmission on the network, with the service providing computational system; wherein a corresponding user input for activating the corresponding instance is received prior to activation of the advertising selector for determining the corresponding advertising presentation; a combiner for obtaining combined data, wherein said combined data is a result of combining at least one of said corresponding advertising presentation presentations with data for displaying at least a portion of said corresponding instance, the portion being transmitted on the network as a response to one of the user interactions, said at least one corresponding advertising presentation including at least one network link for identifying another presentation related to said at least one corresponding advertising presentation, said network link associated with a corresponding one or more locations on a display of said at least one corresponding advertising presentation, wherein a first user input indicative of at least one of said locations activates said network link for presenting said another presentation; wherein said service providing computational system provides substantially a same informational content of the corresponding instance, regardless of which of said advertising presentations are combined therewith; a network interface for (a) and (b) following: (a) transmitting, via the network, and for each user interaction of the user interactions, a corresponding occurrence of said combined data to the first user for display during as a response to the user interactions interaction with said corresponding instance , wherein the at least one corresponding advertising presentation and the informational content for the occurrence, are presented concurrently at the first user's corresponding node ; (b) receiving, from the first user, one or more user data items indicative of an action in response to at least one of the occurrences of said combined data being presented; and one or more user response processing modules for one or more of: evaluating an effectiveness of said corresponding presentation , and obtaining another one of said advertising presentations for providing to said combiner, said processing modules receiving said one or more user data items.