Online advertising revenue in the first half of the year totaled $5.8 billion - 26 percent more than in the first half of 2004, according to a figures issued Monday by the Interactive Advertising Bureau (IAB) and PricewaterhouseCoopers, reportsCNET. Search advertising revenue reached $2.3 billion, or a 27 percent increase over 1H04. Search accounted for 40 percent of revenue, followed by banners and classified at 20 percent and 18 percent, respectively.

Though rich media accounted for only 8 percent of online ad revenue, growth was 26 percent and is expected to continue apace. Sponsorship was the only online category to contract, constituting just 5 percent, down from 9 percent in the first half of last year.

The top-tier publishers loosened their grip on revenues, writes ClickZ. The top 10, 25 and 50 sites lost a few percentage points as advertisers spent a bit more of their budgets on lower-tier publishers, likely including blogs. In 1H04, the top 10 sites accounted for 74 percent of spending; that proportion for 1H05 was 72 percent.

CPM and impression models grew to account for 48 percent, from 45 percent in the first half of 2004; performance deals reached 40 percent from 38 percent; and hybrid revenues were at 12 percent, down from 17 percent.

Email budgets were up more than 60 percent in the first half, but compared with other online formats the figures were negligible - $116 million and a 2 percent share - writes DM News. Last year, email accounted for 2 percent of online ad revenue with $70 million.