• by Wendy Davis , October 13, 2005

Hurricane Katrina spurred a surge in online ads by charities last month, according to new data from Nielsen//NetRatings AdRelevance.

Impressions by public service organizations such as The Red Cross accounted for 14 percent of all ads, up from 6 percent in September of 2004. Within that category, International Red Cross and Red Crescent Societies accounted for 10 percent of all impressions--up from less than 1 percent last September.

Other marketers that advertised heavily online last month included financial service providers, who accounted for 22 percent of impressions in September--up from 19 percent one year ago. Web media, also a big online advertiser, accounted for 16 percent of impressions, from 19 percent a year ago.

Rounding out the top five categories were retail goods and services, which were responsible for 13 percent of impressions--down from 16 percent last year--and telecommunications ads, which represented 9 percent of online impressions--up from 7 percent one year ago.

Overall, marketers served 110.2 billion online impressions last month--down slightly from 112.1 billion in August, according to new data from Nielsen//NetRatings AdRelevance. Until September, the number of ads served this year had been trending upwards since at least April, when 91.4 billion ads were served.

The most popular venue for online ads was MySpace, which accounted for 10.1 percent of all impressions. While that proportion was down slightly from last month's 12.4 percent, it still was up from the 6.3 percent share of ads commanded by MySpace in May.

Yahoo! Mail accounted for 8 percent of online impressions, up marginally from last September's 7.9 percent. MSN Hotmail was the third most popular site for ads, capturing 6.7 percent of them--down from last year's 7.9 percent.

Nielsen//NetRatings AdRelevance doesn't include in the data ads served on proprietary America Online pages, accessed only by AOL subscribers--but counts ads that appear on AOL pages accessed via the Web.