We've seen this one coming all year. Facebook is now the third largest website in the world, taking the No. 3 spot from Yahoo (YHOO), according to comScore. Facebook drew an estimated 648 million unique visitors from across the globe in November, 2010, compared to 630 million for Yahoo. In October the two sites were dead even with 633 million worldwide unique visitors each (actually Facebook had already passed Yahoo by a smidgeon in October with about half a million more visitors). The only two Web properties left which are bigger than Facebook are Microsoft (MSFT) (869 million worldwide visitors) and Google (GOOG) (970 million) when you look at all of their sites collectively.
In the U.S., however, Facebook is still No. 4 in terms of total monthly visitors (with 152 million), and Yahoo is No. 1 (with 181 million). So not all is lost. Note also that these comScore visitor estimates are different than Facebook's official user numbers which are somewhere north of500 million worldwide, but they are better for making apples-to-apples comparisons between sites.