• by Wendy Davis  @wendyndavis, September 15, 2006

Yahoo's mail service captured more than four in 10 online display ads last month--more than any other single site, according to new data from Nielsen//NetRatings AdRelevance.

With 41.4 percent of all display ads, Yahoo Mail accounted for nearly three times as many as the closest competitor--social networking site MySpace, which captured 16.1 percent of display ads. MSN Hotmail was the third most popular ad destination, with 7.8 percent of display ads.

Yahoo Mail not only was the most popular site with advertisers, it also surpassed the 32.9 percent share it garnered in July, and the 7.6 percent market share it drew one year ago.

MySpace accounted for a slightly lower percentage of ads last month than in July, when it drew 18.7 percent--but its August share was still higher than one year ago, when the social networking site accounted for 12.4 percent of online display ads. MSN Hotmail edged up slightly from July (7 percent) and last year (6.6 percent).

Financial services companies were the largest online advertisers last month, accounting for 28 percent of online display ads--an increase from both July (25 percent) and last year (22 percent). Retail goods and services claimed 18 percent of ads, also up from July (17 percent) and last year (16 percent). Rounding out the top three categories was Web media, which accounted for 14 percent of display ads--down from July (18 percent) and last year (18 percent).

The overall number of cost-per-thousand impression display ads tracked by Nielsen//NetRatings AdRelevance totaled 233.5 billion--up from 187.2 in July, 193.6 billion in June, and 197.7 billion in May. The company doesn't track certain types of online advertising, including pre-roll, partnerships and sponsorships. The AdRelevance data does not include ads served on proprietary AOL pages, but counts ads that appear on AOL pages accessed via the Web.