Mar 18, 2011 08:57 GMT  ·  By

February was a relatively slow month for online video, as the number of total viewers was down from the previous month. Of course, the extra three days in January probably contributed to that. Time spent watching and the number of viewing sessions grew though.

As always, YouTube dominates the chart accounting for most of the activity. Microsoft made a big jump in February while new measurements contributed to Facebook gaining share as well.

"Google Sites, driven primarily by video viewing at YouTube.com, ranked as the top online video content property in February with 141.1 million unique viewers," comScore reported.

"Microsoft Sites captured the #2 ranking (up from #7) with 48.8 million viewers, followed by Yahoo! Sites with 46.7 million viewers. Facebook.com came in fourth with nearly 46.7 million viewers, while VEVO ranked fifth with 45.9 million viewers," it said.

"Google Sites had the highest number of viewing sessions with 1.8 billion, and average time spent per viewer at 262 minutes, or 4.4 hours," it added.

While the number of total viewers went down, 169.6 million compared to 171.1 million in January in the US, the number of views grew reaching over five billion views last month. Likewise, the time spent watching online video grew quite significantly, from 816 minutes to 870 minutes per viewer.

Microsoft was the biggest mover, adding about 10 million new viewers. There has been some speculation saying that Bing's growth in the search market contributed to this, but it can't account for such a big increase.

Facebook added more than four million new viewers, but, more importantly, it added about 50 million more views. This is due to new sources being attributed to Facebook, comScore explained.

In terms of video ads, Hulu reigns supreme as always. It served 1.1 billion ads, more than double its closest competitor, an ad network.