• by Joe Mandese  @mp_joemandese, June 29, 2010

The volume of online display ads has expanded 15% over the past year, but conventional banner ads continue to dominate the marketplace, according to new data released this morning by comScore. The report, which is based on April 2010 data, shows that average CPMs also are rising, a phenomenon comScore attributed to "several drivers," including the fact that online advertisers are utilizing larger and "more engaging creative ad formats."

In April, nearly 60% of U.S. display ad impressions were of the standard GIF/JPEG variety, according to comScore's Ad Metrix report. JPEGs accounted for most of that – 42.4% of total ad impressions vs. 14.1% for GIFs.

Flash and rich media ads combined to represent 40.3 percent of all display ads viewed.

In terms of formats, banners accounted for 23.1% of all impressions, followed closely by rectangles (22.7%) and non-standard units (22.1%).

The most common specific ad sizes were medium rectangles (300 x 250 in dimension) at 18.6%, leaderboards (728 x 90) at 18.3%, and buttons (120 x 90) at 14.7%.

Pop-ups and pop-unders now represent less than 1% of all display ad impressions, most likely a function of the pop-up blockers now standard in most browsers.

New Online Publishers Association ad formats, such as the 970 x 418 pushdown and 468 x 648 XXL box, are just beginning to gain adoption and currently account for only 0.1% of impressions.

Display Advertising Creative by Size May 2010 Total U.S. – Home & Work Locations Source: comScore Ad Metrix
	Total Display Ad Impressions (000)	Share of Publisher Ad Impressions
Total Internet	408,621,155	100.0
Banners	94,296,399	23.1
Rectangles	92,646,426	22.7
Non-Standard	90,466,905	22.1
Buttons	84,667,578	20.7
Skyscrapers	43,475,848	10.6
Pop-Ups and Pop-Unders	2,810,584	0.7
OPA Ad Formats	257,415	0.1