Usability testing
"We sit in front of a TV, we listen to the radio, but we use the Web"
In all the usability sessions I have facilitated I've never heard anyone say "I'd prefer this if it was a harder to use".
The Web, unlike TV, radio or print, asks a lot of the user. Every website presents the user with a new interface to learn. The easier we can make your website's interface, the more useful we can make its content and the more chance the user has of doing business with you.
I like to think that the websites I build are appealing but ultimately "invisible". I want users to be able to use your website without having to think about it.
A few usability sessions with a some potential users reap huge rewards and uncover any problems that even the most seasoned designers may not anticipate. I never under-estimate how many great ideas can come from users.