The WWW server replies with any requested resources. The client parses this response and displays it. This interaction often takes a long time, which is called the WWW latency. Large WWW latency may cause user discontent. WWW latency depends on network latency and performance of both servers and clients.
Network latency depends on network bandwidth and propagation delay.
Network bandwidth and host performance can be improved by upgrades. But the propagation delay cannot be eliminated because the speed of light is constant. One solution is caching, a popular technology of WWW proxy servers. A cache stores resources that have been accessed recently. Therefore, caching improves retrieval time of frequently accessed resources.