There is a lack of empirically validated usability evaluation methods that can be applied to models in model-driven Web development. Evaluation of these models allows an early detection of usability problems perceived by the end-user. This motivated us to propose WUEP, a usability inspection method which can be integrated into different model-driven Web development processes. We previously demonstrated how WUEP can effectively be used when following the Object-Oriented Hypermedia method. In order to provide evidences about WUEP's generalizability, this paper presents the operationalization and empirical validation of WUEP into another well-known method: WebML. The effectiveness, efficiency, perceived ease of use, and satisfaction of WUEP were evaluated in comparison to Heuristic Evaluation (HE) from the viewpoint of novice inspectors. The results show that WUEP was more effective and efficient than HE when detecting usability problems on models. Also, inspectors were satisfied when applying WUEP, and found it easier to use than HE. Usability is considered as one of the most important quality factors for Web applications: the ease or difficulty experienced by users largely determines their success or failure [26]. The challenge of developing more usable Web applications has promoted the emergence of a large number of usability evaluation methods [24]. However, most of these approaches only consider usability evaluations after the Web application is fully implemented and deployed. Studies such as that of Matera et al. [20] and Juristo et al. [18] however claim that usability evaluations should also be performed at early stages of the Web development (e.g., at modeling time) in order to detect early how to improve the user experience and decrease maintenance costs. This is in line with the results of a recently performed systematic mapping study on usability evaluation methods for Web applications [9], which revealed a lack of usability evaluation methods that have been empirically validated and that can be properly used to evaluate analysis and design models of a Web application under development.