To provide a web site addition system with a function of promoting the browsing of a homepage by adding a game module to a web page for commodity advertisement browsed through a network.

A game module 12 is added to a homepage 11. The game determines a winner in real time. Right after a game ends, whether the player has won is determined and when the player has won, the customer is given a prize on the spot and added to a winner list. The player plays the game repeatedly and then view the homepage repeatedly, thereby increasing the advertisement effect of the homepage. By displaying the fact of winning on the terminals of participants in real time, the reliance of the participants on the game is made higher. Since customers who has won higher prizes inform many acquaintances of that fact, more customers are prompted to browse the homepage.