To provide a system by which the information of a screen referred by a user is matched with the information to be processed and the request of the user is responded without discrepancy even at the time of performing double clicking or opening a plurality of images.

A session object 22 holding a session ID relating to a series of requests and responses from a client machine is generated, and response data and a data ID uniquely specifying them are generated in the session object 22 in order to respond to a specified request and are stored in a data storage part 18. At the time of receiving a different request from the response data and the data ID imparted to it from the client machine, the received data ID and a temporarily stored data ID are collated, and when they are appropriately collated, the session object 22 generates the response data responding to the request. Also, a new data ID specifying uniquely the response data after being processed is generated.