This article is almost two years old, but it's full of war stories about not only restaurant websites, but restaurants themselves, If you are a great cook, and someone tells you, "You ought to open a restaurant," ask yourself how much money you're ready to lose.
OK... so that's a little pessimistic. Here's another article that lays out what a restaurant website should do for the customer. What do people want to know when they visit your site? Well, how much the food costs, what it looks like, and when you're open... at least, those are my own wild guesses.