This thesis introduces a client-server architecture where customized graphical user interfaces are generated for networked clients with different capabilities. Particularly, it addresses restricted and embedded client devices that have severe limitations in terms of processing power, memory, and input/output interface. On the client side a new virtual machine executes binary user interface packets that are encoded in a new description format. On the server side these customized user interface packets are generated from an abstract user interface specification and a transmitted client profile that describes its capabilities. The proposed concepts do not depend on Java-, XML-, or WAP-based technologies and combine ideas from the areas of client-server architectures, user interfaces, virtual machines, and compiler technology. By trying to save hardware resources on the client side as much as possible the proposed client-server architecture contributes to the emerging initiative called Green Computing.