Something I have noticed with website users is a tendency to go for the first obvious text entry box on a screen when intending to search for something. Generally the users in question are of the generation who did not have the internet growing up, so their perspective is different from a lot of us, but, I am still talking about intelligent, educated people, who are making an effort to use the internet, definitely with email addresses and some history of e-commerce purchases, quite possibly with facebook accounts too.
Why have I observed users who fall into this category making the mistake of trying to use the wrong box to search a site and often getting lost as a result? What mistakes are being made in the interface and in the understanding of these users?