This chapter aims to provide an explanation of the technology underlying e-HR systems. Transmission Control Protocol/Internet Protocol (TCP/IP) is the protocol used by computers communicating within the Internet, and its adoption within internal networks has led to the creation of intranets. Intranets and the Internet are therefore functionally identical, the only difference being that an intranet is a network internal to an organisation while the Internet links computers all over the world using ordinary telephone lines. First- and second- generation intranets use servers that simply retrieve files requested by browsers and send the data back, but third-generation servers must send instructions to databases asking for specific information, retrieve this and send it on to the browser. Fourth-generation pages currently represent the highest level of sophistication. Such systems recognise the user on the basis of their logging in details and then present information on the page that is relevant to that particular person.