Yahoo's first-quarter revenue was below analysts' estimates as the company struggles to accelerate its online advertising business. "Yahoo is amidst a multi-year transformation to return an iconic company to greatness. This quarter, we saw encouraging revenue growth of 8%, with display revenue growing a modest 2% and search growing 20% on a GAAP basis. Our mobile GAAP revenue reached $234 million in Q1, growing 61% year-over-year," said Marissa Mayer, CEO of Yahoo. "We anticipated that we would grow GAAP revenue ahead of revenue ex-TAC and EBITDA, and that's precisely what we saw this quarter. For the next phase of the transformation, we will focus on accelerating our GAAP revenue growth while managing our margins and costs."

Yahoo's GAAP revenue grew this quarter, primarily as a result of the company's performance in search and display. GAAP Revenue was $1,226 million, up 8%.

Yahoo also saw an increase in search volume in Q1 2015, with searches reaching a five-year high. The partnership between Yahoo and Mozilla was key to this volume increase.

Yahoo said display advertising revenue rose 2.3 percent to $463.7 million in the quarter, accounting for roughly 40 percent of its total revenue. Search business revenue was up 19.5 percent year-on-year to $531.7 million.

Net income attributable to Yahoo fell to $21.2 million, or 2 cents per share, for the quarter ended March 31, from $311.6 million, or 29 cents per share, a year earlier.