• Estimates of abandoned shopping carts on e-commerce sites ranged from 65% to 80%

This quote is useful as it suggests most sales don't actually go through which could mean that the shopping cart page or the checkout page is difficult to understand. 

• Compliance with Usability Guidelines by Design Aspect:
  Checkout & Registration 59%
  Search 42%
  Category Pages 51%

This further backs up the first point

• International Users – When US-based sites go global, many aspects of the user experience get broken. This report focuses on not only the obvious issues, such as address formats, but also cultural issues as well. Based on usability tests with 24 European users.
• Nua Internet Surveys (www.nua.ie) estimated that the total number of Internet users in the world was 407 million, of which 167 million were in the United States and Canada. Thus, 59% of the potential users are “international” as far as US websites are concerned.
• Checkout & Registration – Filling out Web forms correctly is very difficult for most users. Forcing people to register during their first purchase is a confusing and frustrating tactic that drives customers away. Better designs mean more customers can complete the shopping process