While publishing content on the World Wide Web has moved within reach of the non-technical mainstream, controlling access to published content still requires expertise in Web server configuration, public-key certification, and a variety of access control mechanisms. Lack of such expertise can result in unnecessary exposure of content published by non-experts, or can force cautious non-experts to leave their content off-line. Recent research has focused on making access control systems more flexible and powerful, but not on making them easier to use. In this paper, we propose a usable access control systems for the World Wide Web, i.e., a system that is easy to use both for content providers (who want to protect their content from unauthorized access) and (authorized) content consumers (who want hassle-free access to such protected content). Our system can be constructed with judicious use of conventional building blocks, such as access control lists and public-key certificates. We...