I majored in HCI(human-computer interaction) and joined Yahoo! Korea in Sep. 2000 as a head of UED(user experience and design). I have involved in research, interaction design, visual design, work process, security, coordination of cross-BU issues and managing the Front Page. I created Trinity Model which deals with three critical elements such as Human, Business and Product. With this basic model, I am trying to explain all the issues about Internet Business ranging from conceptual level to implementation one.