In order to reduce the inequalities of access to scientific knowledge, the Cité des sciences et de l'industrie has created some service complexes for dealing with practical problems, such as the cité des métiers and, more recently, the cité de la santé. A thousand users frequent them daily, in search of a particular tool, an answer to a question, or some light on their situation/job. The documentary resources are organised in five areas (choosing one's course/career, finding employment, finding suitable training, changing one's professional life, creating private activity), and pose problems of rapid obsolescence, scattering, or even lack of suitable works on the subjects in question. The rapid development of supply on the Internet has extended the possibilities of multimedia limits, but it has also made their use by the public much more complicated. To make gateways of thematic sites really accessible is becoming a key issue for this type of centre.