Flow & Pacing
In "The Cutting Edge: The Magic of Movie Editing", the cuts of the scenes within a movie, against each other is as much if not more to the story as is the scenes themselves. Why not, then should the visuals of a site tell the story with the same consideration in mind? Probably because the visitor becomes the editor. While control is relinquished to the individual visitor, the analytics of the site show popular patterns and in those patterns, you can layer the visuals in a pattern or flow that will deliver the story as you intend.