With the proliferation of Web services, quality of service (QoS) becomes a key factor to differentiate the Web services and their providers. In selecting a Web service for use, it is important to consider nonfunctional properties of the Web service so as to satisfy the constraints or requirements of users. In this paper, we present a Web services QoS model which takes non-functional properties into account in various aspects. In this model, Web services qualities are classified into three categories according to the point of view - system-level view, service-level view, and business-level view. We also provide a quality testing mechanism that tests the manageability qualities of our QoS Model