Websites (or more in general interactive applications) need to be evaluated from a usability perspective for improving their quality for the endusers. This paper introduces a systematic methodology called MiLE+ which proposes an innovative approach to usability evaluation under several aspects. The main original feature is the separation between applicationindependent analysis (based on usability principles) and application-dependent analysis (based on the requirements of the application). The paper explores the differences between these types of analysis and presents the activities for carrying them out in an effective way.