For all that the effectiveness of performance testing in terms of the accuracy of load simulation is a common topic of conversation and concern among people and organizations that build or depend on web-based applications, testing a website in such a way as to reliably predict performance is still often more of an art than a science. More than a few brilliant minds have dedicated their careers to this complex topic, and several have published detailed and mathematically sound methods to plan for, predict and model performance characteristics very accurately - as long as there is sufficient empirical data to work from.