I'VE GOT a dot-com success story that will fill your belly -- if not your 401(k). OpenTable.com, an online reservation system launched in 1999, is filling restaurant seats as fast as you can reboot -- giving restaurants a much needed boost in this economic slump and giving diners a hassle-free way to make reservations. In the past nine months, the number of people going to www.opentable.com has tripled. We've all experienced this one: It's early Saturday night and you've just decided to go out for dinner. You think of a place and get excited.

You call, but it's full.

So you call somewhere else, but it's full, too. Actually, everywhere is full. You're stuck. Looks like you're ordering take-out.

Several years ago, Chuck Templeton watched his wife trying to do just this -- make last-minute reservations at their favorite restaurant. That's how his online brainchild was conceived.

OpenTable.com is directly connected to more than 200 top Bay Area restaurants. The system helps manage their reservations and diners can search all 200 restaurants at once for open tables based on such variables as cuisine and location.

It works like this: visit www.opentable.com and check out the restaurants. Become a registered user by filling in your name, e-mail address and birthday. When you make a reservation, it instantly shows up on the restaurant's books. Bay Area restaurants pay $200-$300 dollars a month to be part of the service -- diners use the service for free. The payoff for restaurants is fewer open tables and fuller dining rooms.

According to OpenTable, most of their dining customers spend more than $30 per person. Regular OpenTable diners also accumulate the equivalent of frequent-flyer miles -- and the company is collaborating with restaurants on ways to encourage diners to reserve early or late when dining rooms tend toward empty.

The computer systems that OpenTable leases out allow restaurants to easily track customer requests. Any host, for instance, can instantly see that Ms. A wants that small table by the window, that Mr. B demands his champagne glasses chilled and that there's a birthday at table 25. And computers never forget -- Mr. B will always get chilled glasses. But beware: If you don't make your reservation, that also gets noticed. Three strikes and the registered user will not be able to use OpenTable again.

An inside tip: Because OpenTable automatically sends out confirmation e-mails 24 hours in advance, a large part of cancellations take place in this time frame. So last-minute reservations at a hot restaurant is a real possibility.