The requirements of software are key elements that contribute to the quality and users satisfaction of the final system. In this work, Requirements Engineering (RE) of web sites is presented using an organizational semiotics perspective. They are shown as being part of an organization, with particular practices, rules and views considering stakeholders several differences and opinions. The main contribution of this paper is to relate an experience, from elicitation to validation, showing how organizational semiotics artifacts were exploited in a collaborative and participatory way to RE of a web portal. A case study is described in order to demonstrate the feasibility of using such artifacts to RE when we think about the system as being part of a social organization.