Web interfaces play a very important role in teaching-learning processes in virtual environments, since this is how students carry out their activity. This paper describes a web interface for online learning based on a graphic map that orients learners, tries to reduce cognitive overload, gives access to learning resources and personalizes learning. The interface was designed to guide the learning process in accordance with Shapiro's "site map principle". The objective of this article is to analyze the impact of such web interface on students' satisfaction with the learning process and on their academic performance. We conducted experimental research. The experiment tested the goodness of the interface among students enrolled in a Multimedia Degree in an open university. We used the T-Test, the Chisquare Test and the Kendall correlation Test. The results showed that the interface had a positive impact on students' satisfaction and performance. It also encouraged students to take a more proactive role in their learning activity than with the "normal" interface. These results are in keeping with the features the site map principle has shown in faceto-face environments.