In fact, it was so painful that I wanted to point out that giving a good, qualified web developer or designer the flexibility and resources to go through a few iterations of your project doesn’t mean that you can sabotage him along the way with painful and useless comments.
Keep in mind that you have to balance this with an understanding of your own expertise. If your web developer doesn’t know about website sales conversions then you either need to have that expertise or hire another consultant to provide that direction. Don’t outsource your expertise to an unqualified vendor.
While you work out the details go have a look at some of the other posts by http://theoatmeal.com/. What a great take on web design.