Web applications have become critical components of the global information infrastructure, and it is important that they be validated to ensure their reliability. Therefore, many techniques and tools for validating web applications have been created. Only a few of these techniques, however, have addressed problems of testing the functionality of web applications, and those that do have not fully considered the unique attributes of web applications. In this paper we explore the notion that user session data gathered as users operate web applications can be successfully employed in the testing of those applications, particularly as those applications evolve and experience different usage profiles. We report results of an experiment comparing new and existing test generation techniques for web applications, assessing both the adequacy of the generated tests and their ability to detect faults on a point-of-sale web application. Our results show that user session data can produce test suites as effective overall as those produced by existing white-box techniques, but at less expense. Moreover, the classes of faults detected differ somewhat across approaches, suggesting that the techniques may be complimentary.