In this paper we present an approach for constructing recommender systems that support a user in his navigation through a given Website. This approach is based on a proxy-like architecture that intercepts the user?s requests and the Website answers, analyzes them in respect to an explicit model of the Website and some prototypical uses of it and dynamically generates, in a separate window, a tip and/or an access to additional functionalities related to the Website objective. The paper is illustrated by examples from the construction of a recommender system for a Website proposed by the French Ministry of Research and Education.