Abstract: An electronic commerce method and system for selecting products and creating purchase orders via computer network. The system consists of at least one user operated client computer, and a merchant operated server computer system that processes requests from the client, creates purchase orders, and manages multiple web browser windows within the client. The system features four web browser windows representing four basic functions performed repeatedly and iteratively in purchasing products: “catalog window”, “product window”, “information window”, and “order window”. The system further provides a method to control which window the server output is displayed in to maintain system integrity. The system and method enables the user to switch from one window to another to access any one of the purchasing functions in a single action.