The growing market request for Web Applications is forcing software industries to produce applications under the pressure of a short time-to-market and a strong competition, with the consequence that low quality and poor documented software is often produced. Maintaining, evolving or comprehending these applications are not straightforward tasks, and reverse engineering processes should be defined and validated to support them. In this paper a reverse engineering approach for reconstructing an object-oriented conceptual model of the application domain of a Web Application is presented. The proposed approach defines a process that reconstructs the model in three steps. In each step, heuristic criteria exploiting source code analysis are used for the identification of objects and their relationships. Tools for implementing this method have been produced, and experiments for validating it have been carried out with the support of case studies. Experimental results showed the feasibility and the effectiveness of the proposed approach.