Feb 22, 2011 12:04 GMT  ·  By

Facebook's efforts of becoming a real advertising power are paying off. For the first time, it ranked in the top 10 of most viewed ad networks, according to the most recent ComScore Top 50 U.S. Web Properties report (January 2011, US only data).

Dominating the ad market as expected is Google with a 93.1% reach and 197 million unique visitors.

Second and third are Yahoo and AOL with 85.5% and 85% reach.

Going back six months to August 2010, Facebook had been ranked 26th in the same ComScore Ad Focus ranking. Three months later, in November 2010, Facebook was already on the verge of making the top 10, ranked 11th overall.

While it took another three months to enter the top 10, Facebook's advertising metrics stand in January 2011 at 153 million unique visitors, and a reach of 72.3%.

Judging the brands Facebook has to jump over to reach the top 5, it will take a while for this to happen.

Immediately in front of Facebook is AdBrite, a very powerful ad network at 73.7% reach.

Taking into account that Facebook needed 6 months to grow 2.7% in ad reach, and now stands 1.4% behind AdBrite, it will taken at least 3-4 months to get to the number nine spot if AdBrite stays at 73.7%.

ComScore also ranked the Top 50 Web Properties in January 2011 for the United States, showing the most visited web brands.

The top 5 remained the same as for the last 6 months, with little changes to the top 10.

Number one are Yahoo sites with 178.8 million unique visitors, second are Google sites with 178.5 million unique visitors, third are Microsoft sites with 176.7 million unique visitors, fourth is Facebook.com with 153 million unique visitors and fifth came AOL with 110.9 million unique visitors.

Surprisingly missing from the ComScore Top 50 Web Properties, Twitter.

As for domains of interest, according to ComScore, in January America's main interest when browsing the Web where sites holding information about taxes, travel and jobs.

There's no surprise about the number one spot, since filling a tax report is quite complicated and almost everybody needs some help at one point or another.

To see the rest of the rankings, read the entire ComScore report.