Here’s an infographic that I’ve seen on a few sites (including Shopify and ECWID), that I think clearly illustrates the importance of not just a stable and secure website but also a clear and upfront explanation of costs.
I can think of a few times I’ve made it all the way to “shipping” and decided not to buy because of shipping costs. Or, even worse, I make it all the way to “shipping” to find out the “Free Shipping” offer doesn’t apply to my particular item. :]
Free advice: be upfront about all shipping costs, taxes and fees. Customers will leave if they’re surprised.