REUTERS - July 29 - Facebook expects revenue growth in Q3 and Q4 to "decelerate significantly," sending the social media giant's shares down ~5% in extended trading. The company's total revenue, which primarily consists of ad sales, rose to $29.08B in Q2 from $18.69B a year earlier. The world's largest social network's revenue from advertising rose 56% to $28.58B in Q2. MAU came in at 2.90B, up 7% from the same period last year. Net income rose to $10.4B, or $3.61 per share, from $5.18B, or $1.80 per share, a year earlier.