Early web performance measurement focused on traffic and exposure. Coffey [22] refers to reach measures that estimated “the number of different people who have viewed at least one page on a particular site over the course of the measured month” (p. 2). Such measures were developed by applying traditional advertising practices and methodologies to the Internet [23]. Other early web metrics include clickthrough rates (percentage of visitors who clicked on a link or banner) and conversion rates (percentage of visitors who completed a desired action). The overall usage of a site is typically determined with traffic measures, such as the number of unique visitors, user sessions, page requests or visits (see Bertot et al. [24] and Novak and Hoffman [23] for an overview of traffic measures). For example, Montgomery et al. [25] showed how path information assists in predicting online purchasers