• by Gavin O'Malley  @mp_gavin, May 26, 2011

As further evidence of an industry-wide recovery, domestic Web ad revenues hit $7.3 billion during the first quarter of the year, according to new data from the Interactive Advertising Bureau and PricewaterhouseCoopers. 

Year-over-year, that represented a robust 23% increase, as well as the highest first-quarter revenue level ever.

"I think the growth from [the first quarter of 2010] comes down to a couple of things," explained Joe Laszlo, deputy director at the IAB. "First is a return to the growth trend interactive spending was on prior to the recession."

"But I also believe that marketers and agencies have steadily improved their understanding of interactive advertising and how it can work for both branding and direct response campaigns," Laszlo added. "That is making them increasingly comfortable and confident that ad dollars spent online deliver real results."

David Silverman, a partner at PricewaterhouseCoopers, had his own take on the data. "The year-on-year 23% increase in first-quarter revenues is not just impressive in its own right, but especially so when you take into account the fact that 2010 was a record-breaking year itself for Internet advertising revenue," he said.

Following a dour year in 2009, U.S. online ad spending rebounded strongly in 2010, growing 15% to $26 billion, according to full-year data released earlier this year by the IAB and PWC.

The resurgence in display advertising highlighted the broader online ad recovery. After spending in the category increased just 4% in 2009, it jumped 24% in 2010 to $9.9 billion, accounting for 38% of total revenues.

Within display, sponsorships saw the steepest growth -- rising 88%, followed by digital video (up 40%) and banners (23%). Rich media was essentially flat year-over-year.

Online ad revenue in the fourth quarter of 2010 hit a record $7.4 billion, up from $6.4 billion in the prior quarter.

For the first time, the IAB also recently issued an annual figure for mobile ad spending, which it estimated at $550 million to $650 million in 2010.