(Reuters) – Baidu Inc , China’s biggest Internet search company, forecast current quarter revenue that missed analysts’ average estimate, sending its shares down more than 5 percent in extended trading. For the third quarter, Baidu forecast revenue of 18.17 billion yuan ($2.93 billion) to 18.58 billion yuan, below analysts’ average estimate of 18.79 billion yuan, according to Thomson Reuters I/B/E/S. The company’s net revenue rose to 16.58 billion yuan in the second quarter ended June 30 from about 12 billion yuan a year earlier. Net income attributable to Baidu rose to 3. …