This dissertation focuses on the study of web interfaces, more specifically e-commerce interfaces, identifying the design factors that contribute to its success. We start from the theoretical assumption that the areas of user experience design and visual design are of great importance in the process of construction and use of an interface. From an exploratory approach it is intended to understand and identify which factors regarding design define a successful interface. This purpose is pursued by analyzing a case study, Amazon, and in-depth interviews with a range of experts in the fields of interaction design and visual design. The results obtained confirm the need for the interface to focus first and foremost on users' needs, considering all its components in an integrated and user-centered way. The input of the experts consulted allowed us to identify ten success factors that contribute to the design of a successful e-commerce interface. Regarding the case study, the results also show that, although Amazon is one of the largest e-commerce platforms in the world, certain aspects of the interface design cannot be considered exemplary or referential.