When I search for plane tickets, Kayak is my first stop. I punch in my dates and destination and get a list of prices for that itinerary, which include government taxes, fuel surcharges, and whatever other fees the airline tacks onto it base fares.
Then, since my local airport is serviced by Southwest, and Southwest isn’t included in Kayak listings, I like to check their site too. I enter the same info and get a list of departing and returning flight fares — which do NOT include any taxes or surcharges. This makes a cost comparison between Kayak and Southwest more difficult than it could be.