designm.ag has a great gallery of 26 web designs for the food industry taken from well known companies like McDonald's and Red Robin. If you're looking ideas for great looking restaurant website design, that would be a great place to start.
Restaurant websites share many of the same principles of any website. They need to be user friendly, easy to navigate, have good information hierarchy, and exhibit consistent branding elements from the restaurant itself. While there's endless restaurant concepts, they all have the same goals:
Get people to your restaurant
Get people to your restaurant
Get people to your restaurant
How this is accomplished will vary a bit from restaurant to restaurant, but overall good restaurant website follow the same general formula:
