According to Internet market research company comScore
websites welcomed more than a billion unique visitors around the globe in the month of May 2011, becoming the first Web property in the history of the Internet to reach such a milestone.
"In the past year, Google Sites has seen its audience grow 8 percent to eclipse the 1 billion threshold," comScore said in a blog post. "Microsoft Sites was the second largest Web property in May to reach more than 905 million visitors, followed by Facebook.com with 713.6 million visitors."
Google's feat is particularly remarkable when you consider that seemingly everyone is already using Google to search the Web. The reason the search giant has been able to continually attract new visitors is because of its non-search services, like YouTube and Gmail, both of which played a big role in the 1 billion milestone.
It's also worth mentioning that Google had just shy of 496 million unique visitors in 2006 when comScore first began taking such measurements.