To design an easy-to-use interface, pay attention to what users do, not what they say. Self-reported claims are unreliable, as are user speculations about future behavior.
The user experience design of a product essentially lies between the intentions of the product and the characteristics of your user.
Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.
Any fool can write code that a computer can understand. Good programmers write code that humans can understand.
If you want a great site, you’ve got to test. After you’ve worked on a site for even a few weeks, you can’t see it freshly anymore. You know too much. The only way to find out if it really works is to test it.