Very good question indeed. IMHO it is not counted if it's just plain HTML or PHP or ASP. More or less anyone can do that. Also if you have spent 1,000 hours on it of your own time and multiply that by $10/hr (or $100/hr for that matter) it does not count. Meaning: a buyer will look at what he can make and how long it takes to get his investment back. The rest is irrelevant.
Now if it is something really special in Flash or JSP or CF or XML, it may be worth something but again, the result of the look & feel or programming, will (or should) have its effect on the income of the site so the better the programming, the more income and that determines the value of the site. My 2 cents...