In other categories, Web media ads accounted for 19 percent of online display ads last month--the same proportion as in March 2004. Retail goods and services marketers accounted for 14 percent of online ads--the same percentage as last month, but less than the 16 percent of ads purchased by retailers in March 2004. Impressions from telecoms were responsible for 10 percent of online ads--more than last month's 9 percent and the 8 percent of March 2004. Travel ads represented 7 percent of the online impressions, as was the case last March.

Health-related ads accounted for 3 percent of all impressions, comparable to last March's 4 percent. Within the health category, several large advertisers increased their share of impressions, while others decreased them. One of the largest marketers in the category to show a drop in market share was Weight Watchers International, Inc., which was responsible for 26.7 percent of health-related online ads in March 2004, and only accounted for 14.7 percent last month.

Waterfront Media, Inc., an online publisher of self-help material, only accounted for 3.8 percent of health-related ads, down from 17.4 percent in March 2004. AstraZeneca Pharmaceuticals also decreased its share of ads from 6.9 percent in March 2004 to 2.9 percent last month.

eDiets.com, Inc. increased its online ad share from 16.4 percent in March 2004 to 18.7 percent last month. Other companies to increase their share of impressions included IncreaseYourHealth.com (4.5 percent in March 2004 to 11.4 percent last month), The Reader's Digest Association, Inc. (none in March 2004 to 7.7 percent last month), and Novartis AG (1.6 percent in March 2004 to 7.3 percent last month).

Where did marketers place their Web ads? The three most popular destinations were sites devoted to e-mail, portals, and search engines, and general and national news sites. E-mail sites garnered 18.7 percent of impressions last month, a slightly larger share than last year's 16.7 percent. Portals and search engines captured 15.4 percent of impressions--down from last year's 22 percent--and general and national news sites accounted for 12.1 percent, which was greater than last year's 8.9 percent.

Specifically, MSN Hotmail garnered 7.7 percent of ads, followed by Yahoo! Mail (7 percent), Yahoo! Homepage (3.8 percent), myspace (3.7 percent), eBay (3.7 percent), and Yahoo! Finance (3.2 percent).