So much for the string of record quarterly gains for online ad revenues… The Interactive Advertising Bureau reported that internet ad revs reached $5.8 billion in Q1, an 18.2 percent rise over Q107. But this was the first time in three years that online ads experienced a sequential decline. For the past three years, every quarter brought another record in IAB tallies; this one was the “second highest” after Q407’s $5.9 billion take. The 18.2 percent gain, while healthy, also provides further evidence of how online ad growth has been slowing over the past year: in Q107, the IAB reported 26 percent year-over-year growth.

David Silverman, partner, Assurance, PricewaterhouseCoopers, which helped prepare the IAB report, sought to explain the sequential decline from Q407 to Q108, pointing to the traditional drop in ad spending after the holiday season, along with an overall economic slowdown.

The IAB’s report is in line with other relatively dismal reports looking at online ad growth this week: the Nielsen Monitor-Plus’ report saying that internet ad impressions in Q1 grew by 14.7 percent compared to last year’s 31.9. Before that, the National Newspaper Association said newspapers websites’ Q1 ad revs rose only 7.2 percent versus the 22 percent gains posted the year before; and TNS Media Intelligence found that the quarter’s display ad dollars were down sharply from last year’s double-digit growth rates, but the segment still managed to reach a healthy 8.5 percent gain. In Q107, TNS said that display ads grew 16.7 percent. More details from IAB/PwC here.

• Online Ad Impressions Grew 14 Percent In Q1, As Separate Research Shows Flat Prices In May
• Hard Times For Newspapers Gets Harder, As Q1 Online Ad Growth Stalls At 7.2 Percent Gains
• Display Ads Grew 8.5 Percent In Q1, Down From Last Year’s 16.7 Percent Gain: TNS