Pop quiz: which is the most popular website in the US? For years the correct answer would have been Yahoo, despite everyone thinking it is Google. However, the latest comScore rankings, which list popularity in terms of the unique monthly visitor metric, has Google beating Yahoo for the first time ever. The confusion comes as a result of Google being way ahead of the competition in terms of search visibility, but when you start adding in other web real properties the statistics turn on their heads.

In fairness, the actual scale of the Google lead is miniscule in Internet terms; a mere 466,000 out of a combined head count of something fast approaching 300 million.

The actual figures, to be released officially later today, are:

Google audience in the US for April is 141.1 million, 18 percent up from 12 months back, while Yahoo was also up but only by 7 percent to 140.6 million. To give you some idea of how far ahead in the game these two are, and why Microsoft wanted to buy Yahoo so badly, Microsoft sits in third place some 20 million adrift on 'just' 121 million.

As always though, things are not quite as straightforward as you might think. Because comScore still has Yahoo ahead of Google when it comes to page views which although not as universally recognized as a valid metric for popularity as unique visitors, does mean that either visitors are spending more time on Yahoo than Google or returning time and time again. The lead using this metric is substantial as well, 33.6 billion page views compared to Google on 28.7 billion.