I find that most shopping carts I run across abuse their users for the sake of not performing some very simplistic programming.For example, far too many carts require you to enter your credit card number without any spaces or dashes, ie:
You must enter 6574-1181-1111-1112-2112 as 65741181111111122112! Ok, how many 1's are in here!
What is the purpose here? You can much more easily and accurately enter the number with dashes or spaces in it. Even on your credit card it is printed with spaces.
One must be an extremely lazy or ignorant programming not to include one line of code to remove spaces and dashes (or any non numeric) from the card number.
For just a few minutes of the programmers time you will save thousands or even millions of minutes wasted effort when people try to use your cart. Some will even give up in frustration and spend their hard earned money with someother merchant!