This paper introduces a new web application specification based on G-DEVS M&S, employed here to validate concepts and feasibility, in order to secure its implementa-tion. The application is a web-spider and graph visualization tool; which supplies website metric analyses to the user, i.e. an informetric characterization with a topologic description and also an interactive manipulation of graphs. The tool provides different indicators of consistency of the web site with regards to customizable parameters. The scope of this study aims to improve the quality and attractiveness of public (government offices) and university web portals. There are some technical constraints, i.e. the bandwidth range and DNS (Domain Name Server) definitions; which are also taken into account. This tool has been designed for different kind of users that may range from webmasters through end users. G-DEVS models allow us to specify, test configuration by simulation, test integration of heterogeneous components using G-DEVS/HLA interoperability and thus make the implementation easier and safer, especially when we will save time by avoiding some implementation failures.