The sales of customisable products and services over the internet is a challenging task within the area of electronic commerce. In this chapter we will present a case study which shows how the offering and selling of complex products and services from the telecommunication industry is supported within a generic framework for customer-adaptive distributed online configuration. Following the paradigm of mass customisation, products and services are nowadays sold to customers in many variants according to specific customer requirements. In a Web-based environment special emphasis must be given to the customer interaction with the sales system. Therefore we sketch how a personalised Web-interaction may imitate a good salesperson that adapts his expert advice according to the customers interests and skills. The digital economy of the 21st century will be based on flexibly integrated webs of highly specialised solution providers. Regarding configuration technology itself, the joint configura...