Authors spend a lot of time formulating them, wording them, formatting them. I suspect most readers skip over them without even noticing them, just as we do not notice page numbers when captured by an absorbing novel. Our attention moves directly to the location most likely to contain the information of interest, most likely, that is, in terms of previously established convention, most likely in terms of the mental schema held by the reader. Violate the conceptual model, and you are apt to discover that readers miss critical information. They reaffirm the rule of consistency, coherence, and the following of established conventions.
People use cognitive schemas to guide their attentional focus.
So, web designers, be creative and original at your own peril. You would do better to follow a clear, coherent conceptual model, one consistent with established conventions and genres. The more we know about real human behavior, the better our designs will fit the people they are intended to serve. The Author Together with Jakob Nielsen, Don Norman is a User Advocate, teaching companies how to develop human-centered product development. Guidelines for multimedia on the web.