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So what was the most popular U.S. website last month? Not Google (sort of).

Turns out that Yahoo had the most unique monthly visitors in July, beating even the search king. And that didn't even include numbers for Yahoo's newly acquired Tumblr blogging site, which came in 28th place on rankings from comScore.

Yahoo had 196.6 million monthly uniques versus Google's 192.3 million for Google. However, the numbers do not include mobile usage and visitors are only counted once in a month, no matter how many times they return to the site.

(Read more:Yahoo and Dan Loeb not parting on good terms)

Microsoft, Facebook, AOL and Amazon rounded out the Top 6. Microsoft came in third with 179.6 million unique views, followed by Facebook with 142.3 million.

Ed Barton, director of digital media at technology consulting firm Strategy Analytics, said the numbers were "incredible" and a "pretty strong endorsement" for Yahoo CEO Marissa Mayer.

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"No online media outlet would have come close to predicting this, and if they had, you would have said they were insane," said Barton. "This will probably have a positive impact on the share price and if Yahoo keeps this up, it has a chance of becoming relevant again."





What's Marissa Mayer's plan for Yahoo? Daniel Rosensweig, Chegg president and CEO, and Kara Swisher, All Things Digital, provide a progress report on the CEO's first year at the helm of the tech giant and what investors can expect to see in the future.

Yahoo shares traded higher Thursday, up about 80 percent in the past year. (Click here for the latest price.)

Barton added that the raft of changes Mayer has made since becoming CEO, including the acquisition of Tumblr and the extension of maternity leave benefits, had proved very positive.

(Read more:Tumblr founder to get $81 million to remain at Yahoo)

Mayer said in a recent Vogue interview that Yahoo will thrive in the transition from desktop to smaller screen mobile devices by returning to its "daily habits" roots.

"Email, maps, weather, news, stock quotes, share photos, group communication, sports scores, games. You're listening to what people do on their mobile phones," she told Vogue. "And it sounds like a list of what Yahoo does."

—By CNBC's Jenny Cosgrave: Follow her on Twitter @jenny_cosgrave

Disclosure: CNBC has a content-sharing partnership with Yahoo's finance site.