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 health website operator WebMD (WBMD) soared a whopping 25% today after its quarterly results and guidance topped Wall Street expectations.

So what: The stock was crushed in 2012 as weak ad spending and increased competition pressured results, but a wide fourth-quarter revenue beat -- $132.7 million versus the consensus of $124.1 million -- coupled with positive full-year guidance suggests that things are turning. In fact, total traffic to its websites rose 20%, while unique users per month surged 28%, giving Wall Street plenty of good vibes over its growth prospects going forward.

Now what: For 2013, management now sees a loss of $0.13-$0.45 per share on revenue of $430 million-$455 million, well ahead of the consensus loss of $0.44 per share and a top line of $422 million. "We enter 2013 as a more nimble organization that is well positioned to meet the needs of our users and clients in a dynamic and demanding marketplace," said CEO Cavan Redmond. But while its short-term prospects are certainly looking better, WebMD's still-shaky competitive position continues to make the stock a questionable long-term opportunity.

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