What site is the cheapest to buy airline tickets?

I need to buy two tickets to go from Florida to Minnesota on Friday. I really need the cheapest site to buy airline tickets, and if there is a coupon I can have, even better. Thanks!What site is the cheapest to buy airline tickets?
Please check:

Tips:

a- use flexible dates

b- use alternative airports



http://www.hotwire.com/



http://www.cheapoair.com/



http://www.kayak.com/



http://www.orbitz.com/



http://www.priceline.com/



http://www.expedia.com/default.asp



http://www.farecompare.com/



http://www.bing.com/travel/



http://www.airfarewatchdog.com/



http://www.cheapair.com/
try kayak.com - its a meta search engine and checks out numerous different sites before returning its prices.What site is the cheapest to buy airline tickets?
There are man online search site like travelocity and expedia and they all have coupons for discount try them.You can try a site for free coupons http://freetravel4ever.blogspot.com