In recent years, the availability of server-side, Web-oriented component technologies, such as Enterprise Java Beans, ASP .NET, SOAP, and so forth, has led to profound changes in the scenario of information systems, allowing developers to create enterprise Web applications, that is, highly-dynamic information systems able to deliver a complex amount of functionalities, while running in a Web browser. Among those Web applications, the Web portals are of special interest. Basically, a portal is a Web site collecting related information and/or services from different sources. It is intended to provide features such as personalization, integration of applications and business intelligence, notification (push technology), and infrastructure functionality (Winkler, 2005). Due to their intrinsic advantages, Web portals are becoming an essential support for the activities of lots of organizations, companies and public institutions.