A portal site providing machine 20 obtains web pages provided by websites A–E at regular time intervals, and compares the latest web pages with the old web pages obtained last time. Then, the item-by-item comparison is made between the latest and old web pages to determine the degree of updating of the contents. The portal site providing machine 20 provides a portal page which contains images representing respective sites A–E with corresponding size and arrangement according to the degrees of updating.