The increasing demand for World Wide Web (WWW) services has made document caching a necessity to decrease download times and reduce Internet traffic. To make effective use of caching, an informative decision has to be made as to which documents are to be evicted from the cache in case of cache saturation. This is particularly important in a wireless network, where the size of the client cache at the mobile terminal (MT) is small. Several types of caching are used over the Internet, including client caching, server caching, and more recently, proxy caching. In this article we review some of the well known proxy-caching policies for the Web. We describe these policies, show how they operate, and discuss the main traffic properties they incorporate in their design. We argue that a good caching policy adapts itself to changes in Web workload characteristics. We make a qualitative comparison between these policies after classifying them according to the traffic properties they consider in their designs. Furthermore, we compare a selected subset of these policies using trace-driven simulations.