This paper presents a case study highlighting the best practices for designing and building a web-based auction system using UML (Unified Model Language) and component-based programming. We use the Use Case, Class, Sequence, and Component Diagrams offered by UML for designing the system. This enables new functions to be added and updated easily. Our implementation, with its basis in component-based programming, enabled us to develop a highly maintainable system with a number of reusable components: the MethodofBidding (the bidder can bid at three different frequencies -fast, medium or leisurely), the Certification (Identity verification function) and the RegistrationGood (Product entry function) Components. Further, the system uses intelligent agents that permit fair help to bidders participating in auctions and at the same time achieve maximum profit for the seller. The design and implementation environment, along with the tools used, provide excellent support for the successful development of the system.