The Web environment has shifted from a distributed source of information to a distributed source of service. Service-oriented has become mainstream in software development. Because of this, research into the new theory and methodology of software should be carried out. As a new paradigm, Web components aim at providing support to service-oriented development by enabling automatic discovery, composition, invocation and interoperation of services. We discuss various aspects of Web components and present a concept model of Web components. By means of parameterized contracts, we discuss the introspection of Web components in detail and present an approach to tailoring the service.