Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of DealerTrack (Nasdaq: TRAK) have been derailed today, down by as much as 12%, after the company reported earnings last night.

So what: Revenue in the fourth quarter jumped 47% to $91.3 million, with adjusted net income coming out to $10.3 million, or $0.24 per share. Both figures handily topped the Street's expectations of $84.6 million in sales and a $0.20-per-share profit.

Now what: CEO Mark O'Neil attributed the strong results to healthy auto credit and car sales trends throughout the year. What's really weighing on investors is the company's guidance for the coming year. DealerTrack expects fiscal 2012 to see revenue between $365 million and $372 million, with adjusted net income between $44 million and $47 million, or $0.99 per share to $1.06 per share. Both forecasts fall short compared to what the market was looking for.

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Fool contributor Evan Niu holds no position in any company mentioned. Click here to see his holdings and a short bio. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.