Change location

I use kayak.com a lot and when you open the website, it determines your location and fills in some of the blanks for you. Well for some reason it thinks that I am in Birmingham, Alabama. When in fact I am in Las Vegas. It is not only this website, but since this is the simplest example I thought I would use it. Is there some default setting that I can change to make my MB know that it is in Las Vegas?