Yahoo can not sit silent when its rivals, Google and Microsoft are investing heavily in the online advertising business. The search giant has geared up for yet another acquisition barely a few months after its purchase of Right Media. This time, it is the behavioral ad firm, BlueLithium. The deal is fixed at around $300 million in cash, reports Reuter. BlueLithium is the fifth largest ad network in USA and second in UK with nearly 145 million unique monthly visitors. It tracks behavior of the visitors and provides banner advertising on a network of more than 1,000 sites. If you are regular Yahoo visitor, I guess Yahoo will surveillance your online activities and extend you relevant ads through its number of services like Yahoo Mail, Yahoo Messenger and Yahoo Travel etc. Google is all set to acquire DoubleClick for nearly $3.1 billion. Meanwhile, Microsoft’s aQuantive acquisition is official. The software giant paid $6.1 billion to acquire the ad firm. It is the most expensive acquisition in Microsoft’s corporate history. In this context, the recent acquisition assumes greater significant for Yahoo which has ended the second-quarter with poor financial results and a drop in net income over the same period last year.