If you've booked airline tickets or hotel rooms online, you've probably experienced the following.

You see a bold headline on a website that says an airline ticket is available for $99. You've seen the same route advertised for $140 on other sites. So you go into the website and fill in your name, e-mail address, passport details and choose your flight. As you scroll down to complete your purchase, you discover there's a $20 baggage fee, a $12 fuel surcharge and extra fees for "preferred seats".