Abstract: According to the present invention, a terminal executes a program correlated to content displayed in a window, etc., of a browser operating in the terminal. When the content is loaded into the window, etc., by execution of the program, the terminal registers a callback function by a window.requestAnimationFrame method assigned to the window, etc. When the callback function is invoked, the terminal determines, on the basis of an interval of timestamps at which the callback function is invoked with respect to the window, etc., whether or not the window, etc., is being browsed by a user, and re-registers the callback function by the window.requestAnimationFrame method assigned to the window, etc. The terminal intermittently notifies a server of the result of the determination.