By John Letzing 
 

Facebook Inc. (FB) on Wednesday started making a form of online search advertising, a model popularized by Google Inc. (GOOG), widely available on the social site as it seeks to tap new revenue sources.

The Menlo Park, Calif., Calif., social network has long enabled search on its site, which has garnered more than 950 million users, and has also sold graphical display advertising. But Facebook hasn't previously linked advertising to its search functions in the manner pioneered by Google, which allows users to search the broader Web.

The so-called Sponsored Results search advertising now being offered by Facebook enables the placement of small, text-based ads in front of users that can link them to particular Facebook pages or apps on the site based on a query.

A search on Facebook for "games," for example, now results in a sponsored result that links to the Facebook page for Buffalo Studios' title "Bingo Blitz."

The new advertising model for Facebook has been in testing in recent weeks, and was widely rolled out to users and advertisers on Wednesday. It uses a model whereby advertisers pay when users click on the ads, which are targeted to particular entities on Facebook and not to individual keywords.

Google used a similar model to develop its search-advertising business, which still accounts for a large portion of the Mountain View, Calif. company's annual revenue.

Facebook's move into search advertising comes as the company faces pressure on its stock price following its initial public offering in May.

The IPO initially priced Facebook shares at $38 apiece, though a flawed offering process, questions about the firm's ability to capitalize on mobile users, the willingness of big advertisers to spend heavily on the site and the elapsing of restrictions on insider stock sales have all helped cut into its market value since then.

Facebook shares closed Wednesday at $19.44.

Write to John Letzing at john.letzing@dowjones.com

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