An intermediary web server 2 and a plurality of content web servers 4 each store web site data. Each of a plurality of client apparatus 6 is operable to download web pages from intermediary server 2 and from each content server 4 by communicating with intermediary server 2 and without having to communicate directly with a content server 4. Intermediary server 2 reads communications between each client apparatus 6 and each content server 4. Intermediary server 2 modifies web page data transmitted from a content server 4 to a client 6 firstly by modifying all links defining data to be displayed within the page so that each link has a unique address, and secondly by adding content to be displayed at the client. Intermediary server 2 also identifies requests of a predetermined type sent from a client 6 to a content server 4 and stores a copy of the request.