The invention provides a system where additional services using other sites connected over a network are made available when a content is delivered via a network.According to the invention, when user A receives delivery of a content from a content delivery service server (1) by using a terminal (4), predetermined information is transmitted from the server (1) to user A or a community server (2). With this information, the preferential use of community sites or additional use of services is made available to user A. The preferential use is for example the preferential use of a community site bulletin board. The additional use is re-delivery of delivered contents by using community sites.