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

On Thursday, the stock market kept up its recent track record of volatility, as the S&P 500 jumped more than 1% to regain all of its lost ground from yesterday. Even with the impressive gains for the market at large, several high-profile companies saw even better returns on their shares, with Facebook (META -0.52%), Under Armour (UAA), and Pitney Bowes (PBI 0.95%) all moving sharply higher today.

Facebook jumped 14% on positive reaction to the social-media giant's earnings report yesterday afternoon. Despite extremely ambitious expectations from investors, Facebook delivered a blockbuster performance, with revenue jumping 63%, and earnings per share posting an 82% gain. The company also reached an important milestone, with more than half of its revenue coming from mobile advertising for the first time in Facebook's history. Optimism about the company's future could send the stock to further gains, even at its current record-high levels.

Under Armour soared 23% as shareholders cheered the athletic-apparel company's strong growth in both its fourth-quarter results and its guidance for 2014. The company produced 35% higher sales in the quarter, leading to a 27% jump in profits. Gross margins also picked up, but more importantly for shareholders, Under Armour expects that growth pace to continue, with revenue gains of 22% to 23% producing a similar operating-income gain of between 23% and 24%. With some investors pointing to the company's still-huge international expansion opportunity, bullish investors are optimistic about Under Armour.

Pitney Bowes climbed 19% as the mail-services turned digital-commerce solutions company managed to improve its revenue for the first time in years. Sales gains of 2% were enough to please investors, even despite an 18% drop in net income. Still, shareholders who remember the disappointment of Pitney Bowes' dividend cut from double-digit percentage yields might well be slow to forgive the company even if it does turn out to be bottoming out from a sales standpoint.