Check out the history of Used Car with CARFAX 

The CARFAX Vehicle History Report is becoming the most reliable tool for used car buyers to check out its history. This helps in protecting buyers and sellers from scams and frauds. You can find out the history of over 550 million cars. Simply, put VIN # of the car and the history of car can be found out quickly for odometers, junked cars and accidents.

CARFAX collects the data from various sources such as DMV records, auctions, car rental companies, car leases agencies etc. where odometer readings are collected. For instance, if any car had 50,000 miles on its last inspection and someone is selling you with 30,000 miles, the CARFAX history report will immediately alert you, saving you from any fraud.

CARFAX can tell you if the car was totaled in accidents, flooded, returned as a lemon. Also, if the title was modified from "junk" back to "used" or so on

What is VIN #

Vehicles built after 1981 have a unique 17 character Vehicle Identification Number (VIN) which stores the valuable information about that vehicle's history. The VIN number can be seen on dashboards, driver's side door, in documents and car insurance papers. VIN can also be traced on the websites, if dealers and automobile companies maintain them on their websites.