The lack of usability is a problem for developers and companies: different studies of user behavior on the Web find a low tolerance for unusable sites. There is a simple motivation for this behavior: on the Internet, switching costs - how much effort it takes to switch from one provider to another - are low. If you don't find what you want, the competition is only a couple of mouse clicks away.
Nevertheless, if most people agree about the need of usable web sites, there are no general theories about how web usability should work. If we check the most influential books on this topic we found different usability guidelines coming from authors' experience but no general theories to justify them. The aim of this article is to defining the starting points of a web usability framework based on the viewpoint of ecological realism. The framing assumptions of this new approach are one form of a general theoretical stance, which can be called situativity theory, in which cognitive processes are analyzed as relations between agents and other systems.