Microsoft's online advertising deal with Yahoo and AOL is now fully operational, according to the company. The software maker originally announced its partnership in November, promising high-quality inventory for advertisers and publishers. The three tech giants are partnering together to take on Google, who is currently dominating online display ads.

The agreement will allow each network to offer premium non-reserved online display inventory to advertising customers, while operating their core networks independently. Advertising customers wishing to buy up large chunks of inventory across all the sites will be able to do so easily, something that Microsoft and its partners, Yahoo! and AOL, hope will appeal to marketers. Facebook, which is rapidly becoming a large player in online advertising, isn't part of the partnership, so Google and Facebook are the clear competition here. Microsoft has made its feelings clear about Google several times recently, but it remains to be seen if this new partnership will help it threaten Google's main source of revenue.