Due to the widespread use of the World Wide Web, many organizations are creating web sites and developing web interfaces for their existing information systems. Surprisingly however, there appears to be little evidence that organizations systematically evaluate the usability of their web-based systems. The usability of a web site defines how well and how easily a visitor, without formal training, can use the site. Clearly, better usability will result in more efficient interaction between the user and the site and could have important implications for the acceptance of web-based systems. This paper reviews different usability testing methods and describes how protocol analysis (or "think aloud") can be used to test web site usability.