A portal server having a reverse proxy mechanism for proxying one or more Web applications on a backend server in response to a request for Web content from a user. The reverse proxy mechanism includes a portlet, a set of configuration rules, and a rewriting mechanism. The rewriting mechanism is configured to forward a user request for Web content to a Web application on the backend server, receive a response from the Web application, and rewrite the received response in accordance with the configuration rules. The portlet is configured to produce a content fragment for a portal page from the rewritten response. The configuration rules include rules for rewriting any resource addresses, such as URLs, appearing in the received response from the Web application to point to the portal server rather than to the backend server. The disclosed system allows the portal server to appear to the client as the real content server. The portal server is arranged such that an external Web application, which is running on a separate backend server, is displayed to the user within the boundary of the portlet window on a portal page. The backend server remains behind a firewall and the reverse proxy function of the portlet allows a user to access the Web application on the portal server, without needing (or allowing) the user to have direct access to the backend server and backend application which provide the actual content.