Web site usability is concerned with how easy and intuitive it is for individuals to learn to use and interact with a Web site. It is a measure of the quality of a Web site’s presence, as perceived by users. The usability of Web sites is important, because high usability is associated with a positive attitude toward the Web site and results in higher online transactions. Poorly designed Web sites with low usability, on the other hand, lead to negative financial impacts. Existing approaches to Web site usability include measurement and tracking of parameters, such as response time and task completion time, and software engineering approaches that specify general usability guidelines and common practices during software development. This paper analyzes usability from the point of view of Web site design parameters. An analysis of usability and other design characteristics of 200 Web sites of different kinds revealed that design aspects, such as information content, ease of navigation, download delay, and Web site availability positively influence usability. Web site security and customization were not found to influence usability. The paper explains these results and suggests design strategies for increasing Web site usability.