Revenues from online advertising in the US approached $5.9 billion in the third quarter of 2008, according to a new report from the Interactive Advertising Bureau (IAB).

The organization, which compiled the figures in partnership with PricewaterhouseCoopers, said that this represented an 11 percent increase compared with the same period last year.

Despite this, growth flattened quarter-on-quarter, rising just two percent compared with the three months to June – primarily as a result of the ailing economy, according to IAB president and chief executive Randall Rothenberg.

"Interactive advertising continues to be the most measurable and cost-effective way to reach consumers and we see more and more marketers seeking to harness its power," he went on to add.

Research firm eMarketer has previously predicted that spending on online advertising in the US will grow by 17.4 percent to reach $24.9 billion this year and will eventually rise to $50 billion by 2012.