Yahoo became the first of the big three search engines to include results from popular microblogging service Twitter in its search results, making for a more complicated search engine optimization (SEO) landscape.

Michael Liedtke, writing for the Huffington Post, says that Yahoo will top its search results page with four tabs for news-related topics – direct links to sites, video, photos, and Twitter. The move should offer Yahoo users an improved ability to shape the content received from the search engine, and could help boost Yahoo’s declining numbers.

Search engine optimization (SEO) professionals are keeping a careful eye on Yahoo, as the company prepares to undergo numerous transformations. In addition to the move into social search, Yahoo’s partial merger with Microsoft will see that company’s Bing search engine power searches conducted on Yahoo’s website.

The world of search engine optimization (SEO) has long been aware of the coming integration of Twitter and other social networking content into main search engine results, but the effects of the move by Yahoo remain to be seen.