The world’s largest online social network, with over 400 million registered members, has announced it would end its advertising partnership with Microsoft.

Microsoft has been serving cost-per-click advertising on Facebook to users located in the United States for the past three-years. During the partnership, Facebook would sell its own advertising from it’s in house advertising division to users outside of the U.S.

The Microsoft deal was scheduled for renegotiation this past week, prompting Facebook to drop the software giant in order to sell advertising directly to advertisers.

As of December 2009, Facebook remained the fourth largest web property worldwide. In the same period, Facebook was short by about 120 million monthly global unique visitors shy from becoming the third top web property in the world in terms of unique visitors according to comScore. Currently, Google is the top web property in the world, followed by Microsoft and Yahoo. AOL is now the fifth largest web property in the world, after it was knocked down a level after being replaced by Facebook last summer.

According to comScore, in December 2009, Facebook had 469-million unique global visitors, a 31-million increase just over the pervious month. And Facebook continues to grow exponentially, now generating more page views than Microsoft, and even Yahoo. It now makes sense for the company to cut the middleman and retain all advertising revenue.

Facebook confirmed Microsoft would continue to power part of Facebook’s site search with Microsoft Bing, eventually expanding Bing web search to all Facebook users beyond the United States.

Facebook also unveiled its new home page redesign at the company’s headquarters on Friday, showing off enhancements to the user interface that are aimed at making common tasks such as chatting with friends easier. See the video below for specific information on the new Facebook redesign and new features that are demoed by Facebook Product Manager Peter Deng.