Yahoo! (NASDAQ: YHOO) reported second-quarter earnings yesterday, and despite issuing mixed results, shares have bounced as much as 8.5% higher today. Yahoo! missed analysts' expectations on revenue, but reported greater-than-expected earnings per share. But the real story isn't the numbers, says Motley Fool analyst Matt Argersinger. What's the key to Yahoo!'s outperformance? CEO Marissa Mayer.