E-commerce, today, is a part of human communication and social system, though technical aspects of E-commerce systems are important, there are also social variables which should come to consideration, so any E-commerce system can be viewed from two main view points; Technical and Human/Social. Pure technical solutions can not lead to a successful E-commerce. In order to maximize revenue from online trade, companies must have a usable E-commerce systems and websites, which give customers a real and convenient shopping experience and good customer service. If an E-commerce system supports all the factors mentioned above, it can satisfy customers and persuade them to buy online again. It is not easy to create and maintain a system and website which satisfy customers and makes them loyal, but in the case of fulfilling this goal, satisfied users may spend longer time at website, may revisit website later and also may recommend the website to others. The main issue is how to create such a systems and websites which considered being useable. The objective of research is to evaluate variables, both technical and human/social, affecting usability of systems from customers’ point of view.