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 . the system incorporates a catalog containing a plurality of categories within a single web page and arranged in hierarchical form for efficient single - page access without scrolling . the system further incorporates product selection pages accessed from the catalog in a single action and which enable the user to view and select a plurality of products within a single web page , and submit in a single action said plurality of selected products and the desired quantities of each to the server for purchase . the system and method enable a greatly optimized , much faster and efficient overall purchasing process when compared to prior art , and more particularly where the user orders multiple products in a single order such as in the field of industrial and commercial supplies .