It must be designed so that it compares favorably to other sites. Most sites are designed like print ads. Your teenage son could probably do it given enough time. But what does he know about sophisticated Internet marketing, Wave 3 site creation, and all the other subtleties of web design. Years ago you could probably fix your own car, but I challenge you to work on the electrical system of your Toyota.
Cars are very complex today and so is the Internet.
Don't be deceived by the apparent simplicity. There is a great deal more to creating and marketing an effective web site than you could possibly imagine. If you have a web site up now and you are not getting any response, you know what I mean. Listen and learn the answer. If he can't explain to you what all these terms are, he doesn't understand how to effectively create and market your website on the Internet.