Facebook Cracks ComScore's Top 10 For 'AdFocus'

Facebook in January had 153 million U.S. unique visitors, according to new comScore data, allowing the social site to rank 10th among online advertising networks. While reaching 72 percent of Internet users, the Palo Alto, CA-based company achieved its highest comScore AdFocus ranking to date.

The Reston, VA-based firm's survey placed Facebook at No. 11 for November and December 2010. To better illustrate the site's emergence in the last year, it was 32nd (60 percent reach) in May and 26th in June (66 percent).

For January, the No. 1 slot went to Google Ad Network, with 197 million unique visitors, or 93 percent of the U.S. online market.

Yahoo Network Plus, AOL Advertising, Yahoo Sites, and Google Sites rounded out comScore's top 5 for the AdFocus study.

Minus the ad networks, Facebook ranked 4th among the top 50 Internet properties for unique visitors during January, behind Yahoo, Google, and Microsoft, respectively. Twitter was not among the top 50 properties during the month.

Meanwhile, Google's share has dipped slightly since last fall. The Mountain View, CA-based company's total slipped by 2 million unique visitors since October 2010.