Ajax-based web applications are designed to mimic more traditional desktop applications and require quick response times from the underlying Web services. However, since availability and performance of Web services cannot be guaranteed, response time and overall performance of Ajax-based applications can vary. In this paper we describe a framework for developing autonomic self-healing Web service-based applications that rely on the notion of differentiated services (i.e., services that provide common behavior with variable quality of service) in order to maintain required performance characteristics. We present the expected impact of the framework through the use of a theoretical QN model, demonstrate the framework with an example, and provide an evaluation of the technique.