Performance and in particular providing fast response time is one of the critical issues in Web applications. Web portals are emerging Web applications, providing a single interface to access different sources. Dissatisfaction of users dramatically increases with increasing response time, resulting in abandonment of Web sites. Caching is one of the key techniques that can address the performance of such applications. This book provides an overview of Web caching and introduces the current methods and techniques for caching Web objects. It also provides information on Web portals, their architectures, enabling technologies, and performance issues. Moreover, it discusses the use and short-comings of existing caching techniques in Web portals. This book can help Web users as well as system administrators to understand the concepts of Web caching and portal technology. This book is helpful for content providers and Web developers and helps them make their content and applications more cache-aware and perform better by taking into account caching considerations. This book is also helpful for research students and other researchers who are interested in researching on Web Caching.