Many companies look for ways of improving their sales by advertising themselves. David Reiley speaks about the true effectiveness of the advertising tool on market sales through the web. As an economist and an investigator, he describes the great benefits of experimentation in advertisement techniques, as a source of proving the true impact it has on customers and their purchase decisions. Reiley shows his theory and presents the process and results of an experiment he performed for a retail company. He explains why companies are reluctant to carry out these experiments, and from a scientific approach, points out its importance for the upgrading and evolution of marketing resources.