Google’s websites had more than a billion unique visitors in May, the first time an Internet company has hit that benchmark, according to comScore data released Tuesday.Over the past year, Google’s unique visitors per month have increased 8.4pct to just over one billion. During the same period, Microsoft maintained the No. 2 position with 905 million unique visitors in May, up around 15pct, while Facebook’s count surged by 30pct to about 714 million visitors. In May, Yahoo saw 689 million visitors, up 10.8pct over the past year, though it was surpassed by Facebook in October.