Bankrate Inc. warned its third-quarter results would be well below Wall Street expectations because of adjustments to its insurance leads business, sending the company's shares down 21 percent in after-hours trading Monday.

The company, which publishes personal finance content online, estimated earnings of between 2 to 4 cents per share for the third quarter, on revenue of $115.5 million to $117.5 million.

Excluding items, the company, which went public in June last year, expects to earn between 11 cents and 13 cents per share.

Analysts, on average, are expecting Bankrate to earn 20 cents per share on revenue of $132.7 million, according to Thomson Reuters I/B/E/S.

The company's shares closed at $14.50 on Monday on the New York Stock Exchange. The stock was quoted at $11.51 in late trading.