The decline is a "very big surprise," Sinha said. It's sure to fuel speculation on Wall Street over whether rock-star CEO Mayer has an effective strategy, he says. "Everyone's heard stories about how Marissa Mayer doesn't pander to Madison Avenue, and this is a result of that sort-of lukewarm relationship," said Sinha, who nevertheless rates Yahoo stock a buy. In a webcast conference call, Mayer says the revenue decline was caused by issues that are "short lasting" and "can be corrected" within two quarters. One issue was a slower-than-expected rollout of Yahoo Ad Manager Plus, a new ad-buying portal, she said. "We now understand it will take a little bit longer than we previously thought" to boost revenue via that platform, Mayer said. Yahoo says it expects current-quarter sales excluding TAC of $1.02 billion to $1.06 billion. Analysts have modeled $1.1 billion. Q2 earnings per share minus items rose 5% to 37 cents, missing views by a penny. Net income fell.