There’s a really useful article at the moment on Smashing Magazine which explains a number of usability issues when dealing with e-commerce design.
Here’s the topics it covers:
- A lack of detailed product information
- Hiding Contact Information
- A Long or Confusing Checkout Process
- Requiring an Account to Order
- An Inadequate Site Search Engine
- Poor Customer Service Options
- Tiny Product Images
- Only One Product Image
- A Poor Shopping Cart Design
- Lack of Payment Options
- Not Including Related Products
- Confusing Navigation
- Not Including Shipping Rates
- Not Including Store Policies
- Not Putting Focus on the Products
You can read the full article on all these topics in the following article 15 Common Mistakes in E-Commerce Design.
The subject matter is mainly focused around e-commerce web design but the same principles should apply to a lot of designs so it’s a good check list to consider when building any kind of website.

A good summary.