reve news published an excellent article last week on the importance of buttons on e-commerce sites in making it clear to the customer what they need to press next.
The article points out that many etailers allow too much room for confusion in the mind of the customer over what they need to do and press to make their purchase.

The article says

Make it obvious
Simple one this - if a customer is viewing an item, the button marked 'add to basket' should be unmissable, a clear call to action. Essentially, all buttons which lead the customer along the purchase process should be the most prominent on the page.

Eliminate what's not essential
Bob suggests that customers should only be given what's needed to complete a transaction, so buttons marked 'proceed to checkout' should be prominently displayed, while any other options, like 'continue shopping' should be less prominent.

Clear call to action
Don't have buttons saying anything which may be vague, such as 'submit' - use phrases like 'buy now', place your order'. Don't leave any room for confusion.

Get the full story at reve news