Networked virtual environments (Net-VEs) are a class of applications which allow for cooperation between multiple users within a 3D representation of an environment. We have developed a general platform-webtalk-i-which allows the creation of any of these environments with easy accessibility via the Web, and fully provides for third-party authoring. After several experiments with different applications deployed using this technique (among these, the Italian National Science Museum), we analyzed user response and usage data, in order to design a new architecture-WebTalk-II-for an improved class of Net-VEs. WebTalk-II is able to generate 3D worlds dynamically based on a database with all major 3D formats, defines different sets of cooperation metaphors within users, and is entirely written in Java. We describe both architectures, assessing their flaws and advantages.