The proliferation of different kinds of mobile devices, ranging from personal wireless devices, such as PDAs and smart phones, to small notebooks, is enabling ubiquitous personal computing. However, even if a personal device is able to access to different kinds of information, often it does not represent the best solution to retrieve a stream of data from the Internet or to visualize it with an acceptable quality. This problem is promoting several research efforts oriented to the definition of techniques and network components able to support the migration of working sessions from a device to a more apt one. Research results related to the mobility of hosts are not sufficient to solve the problem of user mobility. The paper presents a protocol built atop HTTP for enabling session hand-off in Web applications, which, by exploiting a proxy-based architecture, is able to work without interventions on existing applications and Web infrastructure.