On-line advertising is booming. Compared to traditional media, such as Press and TV, Web advertising is cheap and offers interesting returns. Thus, it is attracting more and more consideration by the industry. In particular, it is now a consistent part of the marketing mix, that is, the set of different approaches to advertise a product. Data mining based optimization on Web advertising can take place at many different levels. From a data miner perspective, Internet advertising is a very interesting domain as it offers a very large amount of data produced at fast pace with a rich and precise amount of details. It also offers the valuable possibility of live hypothesis testing. Here we discuss an Apriori based optimization experiment we performed on live data. We show how effective such optimization is.