The co-production and sharing of lay knowledge among Internet users have grown. A large variety of communities of interest have contributed to redefine knowledge as a social construction and to ...redefine the mechanisms, elements and modes of knowledge sharing. I will draw on two case studies that were carried out in Italy in what has become commonly referred to as a shift from Web 1.0 to Web 2.0 inside the European funded project SIGIS Strategies of Inclusion: Gender and the Information Society (SIGIS). This project took place from 1 January 2001 to 31 January 2004. The first case study deals with a website on the rare disease Lupus erythematosus, and the second with the forums on the website of the most read Italian women's weekly, Donna Moderna. The ethnographic analysis of the two websites included the application of various methodological tools, among which were non-participant observation, interviews, online surveys and the collection of the messages exchanged in the two sites. Here I will focus on the content analysis of the messages: 1,845 from the first website and 4,287 from the second. The main result is that a practical knowledge deriving from an intertwined process of information, experience and experimentation that supported the decision-making process in users' everyday life emerged. Consequently, the knowledge produced in the vertical axis of specialists' knowledge was complemented by a knowledge produced in the horizontal axis of the peer.
