Microsoft has struck deal to become the exclusive provider of web advertising to Facebook, the social networking site, as both companies try to keep up with industry leaders Google and MySpace.

Financial terms were not disclosed.

The deal, struck after just one week of talks, comes on the heels of a $900m tie-up announced earlier this month between Google, the world's biggest online advertisng company, and MySpace, the world's most popular social networking site.

It is a further sign that big advertisers are beginning to embrace social sites in spite of lingering concerns they may be linked with inappropriate content that could damage their brand.

Find out more about Microsoft's advertising deal with Facebook at MSNBC.com.