Google (GOOG) continued to be the most visited Web site in June also, with nearly 157 million U.S. visitors, according to comScore (SCOR).
Yahoo (YHOO) in Second positions, with 154 million visitors, followed by Microsoft Corp. (MSFT), with 127.4 million. The duo is also-rans to Google for market share of Internet searches. Both companies are launching new efforts in an attempt to reverse the tendency.
Facebook.com moved up two positions to No. 6, its highest ranking yet as the social-networking site continues to catch the attention of new fans.
Meanwhile, the release of Web browser Firefox 3.5, which includes numerous new and improved features, pushed the Mozilla Organization up 13 spots to No. 28.
Twitter.com, a fast-growing site that lets users broadcast short messages to "followers," made its first appearance in comScore's top 50 in June, ranking No. 46 with 20.1 million visitors. "It's hard to believe that Twitter.com had fewer than a million visitors in June 2008, and now attracts more than 20 million visitors a month," said Jack Flanagan, executive vice president of comScore Media Metrix.
Flanagan noted that travel Web sites gained the biggest percentage of visitors last month as Americans began planning summer vacations. Visitors to airline Web sites jumped 22% to 33.2 million, with Southwest Airlines Co. (LUV) visitors growing 64% to 16.4 million.
Online travel agent sites increased 9% to 42.8 million, and Expedia (EXPE) led the category, with 27 million. Orbitz Worldwide (OWW) was next, up 10% to 12.5 million. The total Internet audience was flat at about 193.9 million visitors.