In this paper, we describe a method for discovering knowledge about users on a web site from data composed of demographic descriptions and site navigations. The goal is to obtain knowledge that is useful to answer two types of questions: (1) how do site users visit a web site? (2) Who are these users? Our approach is based on the following idea: the set of all site users can be divided into several coherent subgroups; each subgroup shows both distinct personal characteristics, and a distinct browsing behaviour. We aim at obtaining associations between site usage patterns and personal user descriptions. We call this combined knowledge ’rich navigation patterns’. This knowledge characterizes a precise web site usage and can be used in several applications: prediction of site navigation, recommendations or improvement in site design.