Nearly 1.3 trillion display ads were delivered to U.S. Internet users during the third quarter of this year, representing a 22 percent increase compared to a year ago.

Facebook led all online publishers in Q3 with 297 billion display ad impressions, representing 23.1 percent market share. Facebook’s market share has increased 13.9 percentage points from 9.2 percent in Q3 2009. Yahoo Sites ranked second during the most recent quarter with 140 billion impressions (11.0 percent), followed by Microsoft Sites with 64 billion impressions (5.0 percent) and Fox Interactive Media with 48 billion impressions (3.8 percent).

“The U.S. online display advertising market exhibited considerable strength in the third quarter with nearly 1.3 trillion ad impressions delivered,” said Jeff Hackett, comScore senior vice president.

“Just one year ago we were still in the midst of an advertising recession, but several growth drivers have contributed to sustained improvements over the past few quarters. The ability to buy specific audiences is enabling a greater number of display ads to be delivered on target, display formats are improving at a rapid rate, and the quality of creative is getting better every day. As publishers prove the value of online display ad campaigns, digital should continue to carve out a bigger piece of the advertising pie.”

AT&T ranked as the top online display advertiser in Q3 with 21.1 billion impressions, accounting for 1.6 percent of display ads. Scottrade ranked second with 14.9 billion impressions (1.2 percent), followed by Verizon with 14.6 billion impressions (1.1 percent).