With the ubiquitous availability of browsers and Internet access, the last few years have seen a tremendous growth in the number of applications being developed on the World Wide Web (WWW). Models for analyzing and designing these applications are only just beginning to emerge. In this work, we propose a three-dimensional classification space for WWW applications, consisting of a degree of structure of pages dimension, a degree of support for interrelated events dimension, and a location of processing dimension. Next, we propose usability design metrics for WWW applications along the structure of pages dimension. To measure these, we propose CMU-WEB–a conceptual model that can be used to design WWW applications, such that its schema provide values for the design metrics. This work represents the first effort, to the best of our knowledge, to provide a conceptual model that measures quantifiable metrics that can be used for the design of more usable Web applications, and that can also be used to compare the usability of existing Web applications, without empirical testing.