Internet advertising revenues increased by 23.2% to a record $14.9 billion in the first half of 2011, according to a report by the Interactive Advertising Bureau and PricewaterhouseCoopers. The rate of growth more than doubled year-over-year, as last year’s first-half ad revenues of $12.1 billion had represented an 11.3 percent increase over 2009.

Of all interactive ad spend in the first half of 2011, display-related advertising (banner ads, rich media, digital video and sponsorships) accounted for 37% and search accounted for 49% — both growing at 27% year-over-year.  Digital video increased 42.1%, while lead generation increased 25.4% over the same period in 2010.

“The remarkably resilient performance of interactive advertising so far in 2011 demonstrates that more marketers are placing big bets on digital to tell their brand stories,” said Randall Rothenberg, President and CEO, IAB. “This welcome news, in light of the weakness in a large part of the rest of the U.S. economy, confirms that the innovations happening in interactive marketing deliver great value to the industry and to the consumer.”

“Strong online advertising growth has continued into the first half of 2011,” said David Silverman, a partner at PricewaterhouseCoopers LLP. “Fueling this growth is the ability of advertisers to correlate performance and results with the dollars they are investing.”

“These figures build upon the positive news we saw in the 2010 year-end revenue report,” said Sherrill Mane, Senior Vice President, Industry Services, IAB. “It’s a clear signal that all of us in the interactive advertising industry are delivering meaningful results to marketers—and that they are confident in investing in interactive.”