Quite often, a viewer will get so attracted to one part of the site that he/she accepts that part as the entire target and completely misses the overall picture. This is a situation where the viewer, "Can't see the forest for this @* single tree!". The term originated one day after a session when the viewer and monitor went to the actual site for actual feedback. The viewer walked up to the door, pointed at the doorknob and said, "There it is! That's what I was seeing! It was a doorknob!"
"And that's exactly what you spent an hour describing," the monitor said, "but the target was the house."