Developing fewer features allows you to conserve development resources and spend more time refining those features that users really need. Fewer features mean fewer things to confuse users, less risk of user errors, less description and documentation, and therefore simpler Help content. Removing any one feature automatically increases the usability of the remaining ones.

Even the best designers produce successful products only if their designs solve the right problems. A wonderful interface to the wrong features will fail.

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

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.

On average, when you ask someone to perform a task on a site, they cannot do it. It's not their fault; it's the designer's fault.

The system should speak the users' language, with words, phrases and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order.

Designers are not users.