Important stuff when it comes to all sorts of things. When an e-commerce (or any other) web site is not usable, customers tend to disappear. Jakob Nielsen is a usability expert who is known for his critique against new web technology, frames and stuff that breaks the reason why html is no longer universal between different web browsers. Usability requires only common sense, but every day we see examples where new and incompatible web applications seem to be more important than common sense. Jakob is in favor of fast and efficient web design with minimal graphical elements.