Designing web sites that are responsive to customer needs is a critical prerequisite for the success of online services. Recently, a usability evaluation procedure, based on the Microsoft Usability Guidelines (MUG) has emerged. MUG identifies five design requirements - content, ease of use, made-for-the-medium, emotion, and promotion - that should increase the usability of sites. To date, however, there has been limited research examining why online customers would place more or less importance on these requirements. In addition to demographic characteristics which may help explain customer needs, we propose that psychographic characteristics will also influence usability-related requirements. To develop our research model and hypotheses, we draw from recent usability literature and research in consumer behavior concerned with customers' beliefs about technology, specifically focusing on four beliefs - optimism, innovativeness, discomfort, and insecurity. We present the results of our study, involving 215 subjects, which examined the influence of customer characteristics on usability requirements.