Usability rules the web. Simply stated, if the customer can't find a product, then he or she will not buy it.

The system should always keep users informed about what is going on, through appropriate feedback within reasonable time.

Users are not designers.

Consistency is one of the most powerful usability principles: when things always behave the same, users don't have to worry about what will happen. Instead, they know what will happen based on earlier experience.

Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out, and not be too large.

People have to want to change before there's any chance of helping them do so.

Information Overload = "information pollution"