Online display impressions declined to 91.4 billion in April, from 97.1 billion in March, according to Nielsen/NetRatings' AdRelevance, reports MediaPost. Web media ads accounted for 20 percent of all April impressions - just as in April 2004 - but more than in March, when they accounted for 19 percent of all online display impressions, and more than in February, when they represented 17.9 percent.

The three most popular places for internet ad placements were again email sites, portals and search engines, and general and national news sites. Email sites accounted for 18.2 percent of impressions in April. Portals and search engines captured 15 percent of impressions - down from last year's 19.5 percent. General and national news sites accounted for 12.6 percent.

MSN Hotmail captured 7.7 percent of ads - a decline from last year's 9.6 percent - and Yahoo Mail accounted for 7.3 percent, down from last year's 7.8 percent. Myspace continued to grow in popularity, claiming 4.4 percent of online ad impressions, up from 3.7 percent in March.