They include a wide-length banner that spans the top of a page, which is new; a skyscraper set off to the right or left; a large square box set in the middle of a Web page; and a smaller square unit. Each can display 15-second animations. The IAB said that advertisers can expect to reach about 51 percent of a Web publisher's audience if they support the four ads, which had been up for review by the ad and publisher community for several months.