This paper describes techniques used in a Web-based decision support system to enhance dermatological diagnosis for rural and remote communities. We proposed a technique to improve the query representation and shorten the length of the query process, and a knowledge validation technique to help the domain expert supervise and maintain a consistent knowledge base. Experiments were conducted to test the effectiveness of each technique. Results indicated that the new querying technique improves a decision tree query approach. In addition, the results showed that supervised knowledge updating can improve the identification and handling of ambiguous cases to produce 100% correct classification.