Illustration borrowed from The Oatmeal -- go there to view the full illustration.
It's no secret that most restaurant websites suck. I'm not talking about something as subjective as the look of them, but about the actual content and where you can or, more often than not, can't find information.
As a public service here are a few pinpoints about what could make your restaurant's website a bit more usable for those of us who actually use it:
The first and rather common issue is creating the website using Flash. It might sound like a wonderful idea, until you realize many tend to look up restaurant information on the go, on a cellphone. Flash + cellphones = :( and no workage.
(Also, don't use background music. It makes your site feel like a Geocities page from 1998.)
As far as the important part -- content -- goes, there seem to be some misunderstanding of what people actually look for. Long, glowing, adjective filled prose about how fantastic you think your restaurant is should be hidden away in an about section, not on the frontpage where it usually can be found.
Reserve the frontpage for the information people really need: Opening hours; a phone number; address and a link to a map; a clearly labeled menu link. That kind of stuff.
Commonly we keep finding opening hours under the contact section. Who the hell thought that would be a good idea? And for heaven's sake, make your menu HTML based, not a PDF -- have you tried to download an image drenched PDF on AT&T? Not a pleasant experience.
I mean, I get it; many think Don Draper-style marketing should carry over to restaurant websites, with an emphasis on colorful language and huge photos. It's really a lot simpler than that. Most people want to get in and out of the website as quickly as possible, and have the basic information almost literally screaming in their faces.
Show exactly what the restaurant is through the basic information first and foremost. That will get people into the restaurant. Hide the basics on the site, and another option is only a quick search away.
A few sites around town do get it right. Latah Bistro and South Perry Pizza, for example, have a lot of information on their frontpages with clear links to additional information. Simple yet effective.