Online broker Ameritrade ( AMTD) raised its third-quarter earnings and revenue guidance and offered positive comments on trading activity, lifting the company's stock higher in premarket trading Friday. For the third quarter, revenue is expected to range from $173 million to $197 million. The company projected earnings of 9 cents to 11 cents a share. According to Thomson First Call, analysts expect the company to earn 8 cents a share in the third quarter on revenue of $153.3 million. Ameritrade also said it opened 31,000 new accounts in May, taking the total to 2.94 million, with an average daily volume of 157,000 trades. The company said the improvement in trade volume in May has carried over into June, as average daily trades have increased more than 25% so far this month. Shares of Ameritrade were getting a boost from the news, adding 76 cents, or 9%, to $8.89 on Instinet before the opening bell.