While there have been research efforts in organizing largescale web videos into topics, efficient browsing of web video topics remains a challenging problem not yet addressed. The related issues include how to efficiently browse and track the evolution of topics and eventually locate the videos of interest. In this paper, we introduce a novel interface for visualizing video topics as evolution trajectories. The trajectory visualization is capable of highlighting milestone events and depicting the topical hotness over time. The interface also allows multi-level browsing from topics to events and to videos, resulting in search exploration could be more efficiently conducted to locate videos of interest. In addition, recommendation of topics accordingly to three-hots: content-hot, evolution-hot and potential-hot, can be easily supported by our system. A user study on three months' YouTube videos using our interface demonstrates the efficiency of our system in browsing web videos. Ca...