For every site you visit there are certain expectations that you bring with you. Because of these expectations, shopping carts should be as simple and straight forward as possible. You’ve already convinced your customer to buy so don’t deter them at the last moment. Instead, fulfill their expectations.
Recently our Conversion Analyst team came across this shopping cart:
Despite the fact that the error was in bolded lettering, it stumped several people when they came to the point of checking out and forking over their money. Many of us immediately clicked the “Update Total” button only to return back to this screen. Others tried valiantly to find this illusive “Proceed to Checkout” button mentioned at the top of the page, but to no avail. The problem was I had not entered in the minimum number of bottles of wine into my cart, but rather than focusing on the message that was in plain English in front of me, I, and the rest of the team (all smart folks), focused upon the lack of a call of action button.
Bottom line: Visitor expectations were not met. Give your customers what they want, even if it’s “wrong.” If the “Proceed to Checkout” button was made available, perhaps, I would not have spent more time reading the error message rather than searching for something that I was prepared to buy.