With total ad expenditures of $72.59 billion for the period marking a decline of 0.3%, an unusually wide variation occurred across media types. Internet display advertising jumped to 7.6% of total expenditures, up from 6.4% a year ago. Magazines were the only other category registering a gain, up 0.9% to 20% of ad spending at $14.55 billion.

For the first time, Internet display advertising was the dominant media category in financial services with 21.6% of all measured advertising spending, said Jon Swallen, senior vice president of research for TNS MI.

"It's a significant thing," Swallen said, adding that the current instability in the subprime mortgage markets will not necessarily translate into an end-of-year decline in Internet ad spending for the category.

Leading the Internet ad spenders for January through June was LendingTree.com, which spent $120.999 million on display advertising. The next closest spender was University of Phoenix Online at $79.4 million for the period.

In addition, Swallen said, the first half of the year saw a surge in display advertising spending among the top 50 advertisers that account for one-third of all ad spending. Their Internet budgets increased by 58% year-over-year for the period, as compared to the 17.8% benchmark for all spending.

"With this surge, I do think it's real," Swallen added. "I don't think it's a blip."

Still, few have cracked the top 25 Internet display spenders, which continue to be dominated by online-only and direct businesses.

Top 25 Internet Display Advertisers (First Half 2007)