According to the Semiotic Engineering, the human-computer interaction is a way of communication between designers and users. The Communicability Evaluation Method (CEM) is a technique to assess this communication and determine the degree in which the designers achieve to convey users their design intents through the system interface. Most case studies that are described in the literature are focused on the evaluation of desktop applications. In this study, we present the results of a communicability evaluation to a transactional Web application. The experimental case was run by three specialists in the field of HCI and involved the participation of four university students from two academic programs in Computing. These users had to perform some tasks that were developed based on the results of a previous work. After an analysis of the interactions, we concluded that the Website can be difficult to use by users with no experience in the use of this type of software. There are certain aspects of the interface design that should be improved.