It's an offer you can't resist: fly Alaska Airlines to Honolulu for $200 round trip. But what you might not know is that the offer was designed especially for you. Alaska Airlines has introduced a system that creates unique prices and ads for people as they surf the Internet. The system identifies consumers by their computers, using a small piece of code known as a cookie. It then combines detailed data from several sources to paint a picture of who's sitting on the other side of the screen. When the person clicks on an ads, the system quickly analyzes the data to assess how price-sensitive customers seem to be. Then, in an instant, one customer get an offer for a flight from Seattle to Portland for $99 and another is quoted $109. Or someone who had visited Alaska Airlines' site frequently but then abruptly stopped visiting might be greeted with the $200 Hawaii offer. "I guarantee you there are a lot of people who will say yes to that", says Marston Gould, director of customer relationship management and online marketing for Alaska Airlines.