I came accross a very good thread on WebmasterWorld here’s how it starts :

There is no need to prioritize this list, any one of the items listed below will make me abandon the checkout process and go elsewhere. I should add though, that I shop on the Web a lot. What about those new folks out there, or people that are less sure about the Web and CC purchases than I am? Or you are?Ask for too much information. Force me to fill in checkboxes yes/no that are unrelated to my purchase.

Don’t supply a format clue and then refuse my format. Phone #? 555-123-4567 REFUSED. Please, don’t add dashes.

Refuse my zip code. Don’t laugh, it’s happened twice with major airlines in the last two months.

Offer free shipping, right up until the CC authorization, then inform me that I need to spend X amount to get free shipping.

Require more than three pages of information. Sorry, more than three pages is like homework, I want to make a purchase.

500 server error. I’m gone.

Require my phone number. Sorry, I’m giving you my CC#, name, address and shipping info, you don’t need my phone number.

Tell me it’s a secured transaction yet the url shows http://

Show me ‘other offers’ before I can check out. (interstitials, pop-ups, etc)

Don’t save my information, then not provide a format clue, then make me re-enter ALL of my information.

Force me to choose a ‘unique’ user name, and then force me to enter more than two names.

Don’t allow for easy deletion of shopping cart items.

Or, force me to put all my info back in to add something to the cart.

Force me to provide a fax number.

Force me to provide day/evening phone #s, or worse, UNIQUE day/evening phone numbers.

Refuse my coupon code.

I’m sure there are more, this is just MY list. I haven’t even mentioned the aggravations…

Care to add to the list?

I think it’s a very good read for everyone that manages a shopping cart or that sells anything online.  I have seen those errors too many times ! And it’s true that most of the times I closed my browser and stopped the buying process.