⟩ What research has been helpful for both web marketers and their customers?
Any web marketing research shall benefit both web marketers and their customers. As I describe in the article What Can I do For You?, marketing is not about selling. The real marketing is about understanding what your customers need and try to provide superior services or products to meet your customers' needs. Therefore the function of marketing research is to understand what customers need and to gather information for web businesses to provide exactly what customers need.
For example, if a site owner is able to understand why people visit his/her site and why they come back again (from the survey results of SiteSurv, for example), they will be able to develop more effective strategies. Visitors are happy because the site provides what they want, and the navigation on the site is easier.