Visual social network Pinterest broke into comScore’s ranking of the top 50 Web properties -- at No. 50 -- with 25.3 million unique visitors in September. That represents more than tenfold growth from a year ago, when the site had a monthly audience of just 2 million.

Pinterest’s rising popularity appeared to stall in the spring when its traffic was stuck at about 20 million from April to June. But it jumped to 23 million in July and has continued to rise steadily upward. Breaking into comScore's top 50 should also give the company a new marketing tool -- if it can stay in that exclusive club in the coming months.

Google, Microsoft and Yahoo were the top three sites overall with traffic of 187 million, 167 million and 164 million, respectively. Not far behind was Facebook, with 150 million. ESPN moved up six spots to No. 23, reflecting a 24% spike in traffic in connection with the start of the football season.

NFL.com was the top-gaining site overall in September, with traffic jumping 40% to 28 million, followed by ABC Television -- also up 40%, to 7 million -- and Pearson Education -- up 39% to 21.4 million.