I present three essays on online advertising and promotion effectiveness, focusing on how firms make decisions, and how consumer response can be more accurately measured. In the first chapter, I present a cost effective method for measuring online display advertising's impact, net of biases stemming from individual targeting and browsing behavior. I find that the recommended approach can produce dramatically different results from standard correlational measures, and that consumer responses vary greatly with their existing relationship with the firm. In the second two chapters, I examine online daily deals, both in terms of how firms make decisi ons, and how these promotions impact online reviews. The results indicate that these offers have strong, negative, and temporary effects on a firm's reputation, while offering a significant increase in traffic. Further, firms trade-off between these two when deciding whether or not to offer a daily deal.