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 Priceline.com (Nasdaq: PCLN) rose nearly 12% in early trading and remained up more than 8% as of this writing. Last night, the online travel agent reported strong second-quarter profits and gave upbeat Q3 earnings guidance.

So what: Negotiating works. Second-quarter revenue rose 44% to $1.1 billion, while adjusted profit soared 79% to $5.49 a share. Analysts had been calling for just $4.87 a share on $1.07 billion in revenue, according to data compiled by Yahoo! Finance.

Now what: Guidance is what thrilled investors. Management told analysts to expect $9.10 to $9.30 in adjusted Q3 earnings, well above the $7.94 they had projected. Growth like that isn't easy to come by. So while I can't call Priceline.com cheap -- no stock trading for more than 25 times forward earnings ever is -- a 1.09 PEG ratio says this is a five-star stock trading at a three-star valuation. Do you agree? Disagree? Weigh in using the comments box below.

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Fool contributor Tim Beyers is a member of the Motley Fool Rule Breakers stock-picking team. He didn't own shares in any of the companies mentioned in this article at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Google+ or Twitter, where he goes by @milehighfool. You can also get his insights delivered directly to your RSS reader.

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