Abstract: This invention relates to a computer network system, as well as to the instruments and apparatuses allowing the execution of the related methods of operation, comprising a main server computer (10) connected to a communication network (20) to which a CDN (Content Delivery Network) sub-system (70) of server computers is also connected for delivering multimedia contents, and a plurality of user client devices (40, 50, 60) capable to connect to the communication network (20), each user client device (40, 50, 60) being adapted to execute a browser software module (400) comprising temporary storage or caching mechanisms, the browser software module (400) being adapted to connect with a first interface software module (100) executed by the main server computer (10) for visiting a web site of a promotional campaign comprising one or more interactive graphic interfaces (3100; 3200), each interactive graphic interface comprising static data including said multimedia contents, one or more graphic elements (3210; 3230)