In April, Yahoo led the pack with 105.4 million unique U.S. visitors, an 11 percent increase from last year, according to Nielsen/NetRatings Inc. MSN ranked second with 92.8 million visitors, a 6 percent increase from last year, followed closed by Google, whose traffic surged 27 percent during the past year to 92.1 million. AOL's traffic remained flat at 70.4 million, Nielsen/NetRatings said.
Meanwhile, MySpace's traffic -- consisting mostly of teens and young adults -- has more than quadrupled during the past year to 38.4 million U.S. visitors. What's more, MySpace's visitors viewed a total of 19 billion pages on the site in April, surpassing Google (11.9 billion pages), MSN (11.5 billion pages) and AOL (6.8 billion pages).
Yahoo remains the Web's most viewed site, serving up 31.2 billion pages in April, but some analysts believe MySpace's rapid growth foreshadows a changing of the guard.
"The bar keeps getting raised," said Gartner Inc. analyst Mike McGuire. "I think you are going to see constant tweaking because of sites like MySpace."
Remaining the most trafficked and viewed Web site is important to Yahoo because those measures are critical to the advertisers that provide the company with most of its profits.
As it is, Yahoo's earnings haven't been growing rapidly as Google's -- a factor that has weighed on Yahoo's stock price, which has dropped by 21 percent so far this year. Meanwhile, Google's stock price has declined by 9 percent.
Yahoo's shares rose 7 cents to $31.10 in early trading on the Nasdaq Stock Market, where Google's shares fell $2.34 to $373.86.