Facebook crept past Microsoft in the UK for the first time last month, when it became more popular than every other site surfed in the country with the exception of web kingpin Google.
It claimed the second spot in May by notching up 26.8 million visitors, according to online measurement outfit UKOM/Nielsen.
That compares with Microsoft's 26.2 million users, who accessed Redmond's online estate of MSN, Windows Live and Bing last month.
Google remained comfortably ahead of the pack, with 33.9 million UK visitors in May.
Meanwhile, worldwide usage of Facebook has reportedly shot up, even as around six million Americans recently unplugged themselves from the dominant social network.
Facebook, which is run by founder Mark Zuckerberg, hasn't officially confirmed that it now has 750 million users globally.
But it might jump in with a figure soon, given that it announced it had passed the 500 million milestone last summer.
Inside Facebook Gold said earlier this month that around 100,000 UK Facebookers had in fact quit the service.
That claim prompted Facebook to grumble about the growth slump report, while failing to offer up any stats of its own. ®