Revenue from display ads fell 11% year over year, Yahoo said today in reporting first-quarter earnings, and overall declining sales for a second quarter in a row had the stock down about 4% after hours before bouncing back slightly. The stock has gained more than 50% since CEO Marissa Mayer was hired last July. Excluding Korea, the company’s total number of ads sold dropped 7%, though search ad revenue was up 6%. Yahoo also projected net revenue for Q2 to be lower than what analysts had expected, not helping the stock’s after-hours performance (it closed at  Overall for the year’s first three months, the Internet giant reported a profit of $390M, or 35 cents a share, compared with $286M, or 23 cents, a year ago. Net revenue was $1.07B, flat with Q1 2012 but toward the low end of analysts’ estimates.