Yahoo! has introduced two new ad units – Billboard ads, which will position a single rich media ad at the top of the Yahoo! Hompeage, and the mobile-focused Stream ads.

Stream ads will be embedded in the redesigned sites content stream, which is personalised to individual users preferences. Theyre similar to the sponsored content introduced by social networks.

“Since we launched our Yahoo! news stream in February, our users have responded by visiting more, staying longer, and increasing their engagement with our content,” said Yahoo! CEO Marissa Mayer. “Like with web search, users appreciate complementary, unobtrusive advertising, and we’re committed to delivering just that. Advertising can, and should, enhance content discovery in a seamless and effective manner. The more our users spend time with Yahoo!, the more relevant and personalized the content and advertising becomes. Stream Ads are the sponsored twin to our newsfeed articles and are every bit as personalized and engaging.”

Tying into the announcement that Yahoo! will be launching a variety of online original programming, it also unveiled a video ad buying method that blends its topical video channels with distribution partners video content, to create category-specific channels.