A user-centered approach in the development lifecycle of e- commerce websites is nowadays a crucial factor in the success of any on-line business. The purpose of this paper is twofold: a) to identify the factors that affect e-commerce website usability and b) to analyze the role of those factors in increasing the effectiveness of e-commerce web sites. Furthermore, it presents the application of a Multicriteria Satisfaction Analysis (MUSA) method to rank usability attributes in websites based on their competitiveness importance. A case study in eight e-tourism web-sites is presented as a demonstration of this work, the outcome of which will help usability specialists and e-commerce website developers to determine specific usability attributes that are more crucial to the overall usability and user satisfaction of a website. The results of the proposed approach suggest that for each e-commerce website certain usability attributes are likely to be more crucial to the success of the e-commerce website than others. Therefore, identifying the relevant usability attributes in advance through customers’ feedback can be a great advantage to website developers if they want to have an edge over other competitors.