Abstract: A commerce system for computer-based trading is disclosed. The system allows a user to interact with one or more vendors' e-commerce servers. The system comprising a relay server, that is operative to transfer page requests from a user to a vendor's e-commerce server, and transfer page data from the vendor's e-commerce server to the user having applied transforms to data received form the vendor's e-commerce server. The relay server is also operative to process purchase requests generated by a user to relating to e-commerce transactions with the vendor's server. In particular embodiments, the relay server can maintain a virtual shopping basket that contains items selected for purchase from several vendors' sites and can implement payment for these items in a single payment process.