A used car lot.
A used car lot. - 
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Classified Ventures, a consortium of newspapers and media holding companies, is trying to sell Cars.com for a cool $3 billion.

Cars.com started as an experiment by traditional media companies in the late 1990s who saw falling ad revenue from classifieds as people started using online sources for both buying items and doing research.

"That was the time we saw that move from print to online," says Bernard Swiecki of the Center for Automotive Research. "It was also when the online sources of information were gaining traction as reputable."

Because Cars.com snatched a great web domain name, and because it came along at just the right time, it was able to grow into a major presence in online car research. It became profitable primarily because it was able to capture a very specific demographic: people who are interested in buying cars. Advertisers and car dealers are very interested in targeting that group, for obvious reasons.