Q. I recently went on United's web site to purchase airfare from Honolulu to San Francisco and found what I thought was a good fare. I planned to use an "e-certificate" for $150, but I didn't buy the fare. The following morning, I searched again, but the prices returned to me were $100 more than the previous night. I then used a different computer to pull up the information again and the price was the same as the night before. Do airline websites have the capability of "remember" the computers that have visited previously and "adjusting" price accordingly? Perhaps this had something to do with the e-certificate?

A. Web sites definitely recognize your computer from previous visits, unless you clear cookies or other private data (it's easy to do). Airfarewatchdog fare researchers have noticed, when using Travelocity, that if they research a fare, click on it, don't book it, but then look at the same route a few minutes later, the lowest fare they found previously will not show up. Why is this? It might be that airfare search sites figure that if you've looked a fare over but didn't like it for some reason, then they'll show you the next best fare (as in, look buddy, you keep searching for this trip and obviously really want to fly this route, you'll probably pay more if you think there's a chance the fare may increase again)? In any case, it's a good idea to clear your cookies between fare searches (and in fact, it's a good computer "housekeeping" from time to time, no matter what you're searching for).