Conducting business on the Web is an electronic marketing activity. The importance of the use of Web technology for electronic commerce (EC) activities has been discussed widely. Many researchers have identified various factors influencing web site success. This research aims to explore and evaluate factors affecting success of Iranian e-commerce web sites. This research starts with a background of electronic markets and the use of web sites in this specific area then, measuring tools of a successful web site will be discussed. Models which discuss factors effecting web site quality will be introduced afterwards. Furthermore, the methodology used in this research is introduced and the findings and final results will be presented afterwards. A structured questionnaire based on pair wise comparisons was designed, pre-tested, modified, and used to capture data on e-commerce web sites in Iran. Web masters of Iranian e-commerce web sites were chosen to take part in this research's survey. Fuzzy analytic hierarchy process was used to analyze the questionnaires. The explored factors include quality of information and service, system use, playfulness, system design quality and trustworthiness. Each of these factors consists of several sub-factors. By using FAHP the final ranking of these sub-factors in regard to their level of importance is presented. The findings show that providing relevant, accurate and up-to-date information plays the most important role in Iranian e-commerce web sites and the web merchant's benevolence has the least importance in Iranian online market. The final ranking of factors affecting web site success gives the Iranian online companies a roadmap to reach customer satisfaction and profitability