A quantitative method of mapping the web usage of an innovative educational portal is applied to analyze the behaviour of users of the COSMOS Science Education Portal. The COSMOS Portal contains user-generated resources (that are uploaded by its users). It has been designed to support a science teacher's search, retrieval and access to both, scientific and educational resources. It also aims to introduce in and familiarize teachers with an innovative methodology for designing, expressing and representing educational practices in a commonly understandable way through the use of user-friendly authoring tools that are available through the portal. As a new science education portal that includes user-generated content, the COSMOS Portal encounters the well-known "new product/service challenge": to convince the users to use its tools, which facilitate quite fast lesson planning and lesson preparation activities. To respond to this challenge, the COSMOS Portal operators implemented a validation process by analyzing the usage data of the portal in a 10 month time-period. The data analyzed comprised: (a) the temporal evolution of the number of contributors and the amount of content uploaded to the COSMOS Portal; (b) the number of portal visitors (categorized as all-visitors, new-visitors, and returning-visitors) and (c) visitor loyalty parameters (such as page-views; pages/visit; average time on site; depth of visit; length of visit). The data is augmented with data associated with the usage context (e.g. the time of day when most of the activities in the portal take place). The quantitative results indicate that the exponential growth of the contributors to the COSMOS Portal is followed by an exponential growth of the uploaded content. Furthermore, the web usage statistics demonstrate significant changes in users' behaviour during the period under study, with returning visitors using the COSMOS Portal more frequently, mainly for lesson planning and preparation (in the afternoon hours). The findings demonstrate that the new COSMOS users follow the "law of surfing" behaviour, a common pattern of surfing behaviour in portals. However, users return to the COSMOS Portal: returning users comprise more than 50% of all COSMOS visits, stay longer on site and visit more pages. Returning visitors are benchmarked against the "law of surfing" and outperform it substantially. These quantitative results benchmark the web usage of a portal and provide its operators with maps of value-added patterns of the portal's offering to its users in the science education community.