U.S. stocks open mixed amid earnings

U.S. stocks opened mixed on Friday, after three days of losses, as investors considered mixed earnings.

In corporate news, Amazon.com shares jumped over 17 percent in the early trading on Friday, a day after the online retailer posted an unexpected quarterly profit.

The e-commerce firm's net sales increased 20 percent to 23.18 billion U.S. dollars in the second quarter 2015, compared with 19.34 billion dollars in second quarter 2014. Operating income was 464 million dollars in the second quarter, compared with operating loss of 15 million dollars in second quarter 2014.

Starbucks shares rose 3.07 percent to 58.29 dollars per share in the early session after the world's famous coffee chain reported a better-than-expected quarterly profit.

The company's global comparable store quarterly sales increased 7 percent, driven by a 4-percent rise in traffic. Its quarterly consolidated operating income up 22 percent to 938.6 million dollars.

Shares of Biogen, however, fell over 17 percent in the morning session after the biotechnology company lowered its full-year guidance. Its second-quarter revenue also missed market estimate.

Shortly after the opening bell, the Dow Jones Industrial Average was down 21.78 points, or 0.12 percent, to 17,710.14. The S&P 500 shed 3.20 points, or 0.15 percent, to 2,098.95. The Nasdaq Composite Index ticked up 2.09 points, or 0.04 percent, to 5,148.50.

U.S. stocks declined for the third straight session Thursday as investors meditated on a raft of largely lackluster earnings reports. Endi