Facebook Inc. is getting support from two big-name advertisers after tough questions over the effectiveness of its ads.

On Tuesday, Ford Motor Co. and Coca-Cola Co. separately said they found value in Facebook advertising and Ford plans to expand its use of the social network in advertising. The remarks amounted to major-player endorsements for Facebook's advertising business in the wake of the social network's disappointing initial public offering last month.

Ford's global sales and marketing vice president, Jim Farley, said the auto maker is deepening its use of social media, particularly on Facebook, to improve its image among potential buyers. 'Someone who 'likes' you on Facebook is substantially more willing to advocate the brand,' he said at an event in Dearborn, Mich., on Tuesday.

Meanwhile, Coca-Cola marketing chief Joe Tripodi said at an advertising conference in Cannes, France, that was also attended by Facebook executives that Facebook ads probably help drive its beverage sales. 'If we can get 40-million plus fans, or even some subset of them talking positively about the things we're doing, ultimately that's a good thing for us,' he said.

The support comes as Facebook has been fighting concerns that ads on its site don't increase product sales -- and whether the results can be properly measured. The issue was exacerbated last month when General Motors Co. ended a $10 million campaign, declaring that Facebook's paid ads didn't impact consumer car purchases.

At the time, Facebook was under an IPO-imposed quiet period and was prohibited from publicly discussing its business. Since the quiet period lifted a week ago, however, the Menlo Park, Calif., company has vigorously defended its ads. Last week, research firm comScore Inc. released a study commissioned by Facebook that concluded that being a fan of a brand on Facebook causes people to purchase that brand more frequently.

Brad Smallwood, Facebook's head of measurement and insight, has said that the company is getting more aggressive in trying to prove the value of its advertising to clients. The initiative started about six months ago and involved a group of top clients to advise Facebook on how it could do better.

Mr. Smallwood said clients agreed Facebook hadn't done enough to prove its value to marketers. 'We need to be accelerating that learning,' he said.

A Facebook spokesman said the company didn't ask Coke and Ford to make specific comments. Both companies are part of the small group of clients that advise Facebook on improving its ad business, he said.

Facebook counts on online ads to fuel its revenue growth. The company generated $3.1 billion in ad revenue last year, about 85% of its overall revenue.

Facebook currently provides paid and free marketing opportunities to advertisers. Through Facebook Pages, brands can build a following of fans and then post updates that show up in those fans' News Feed. Facebook has started offering advertisers the ability to pay so that more fans see the posts. It also encourages brands to supplement free marketing efforts with paid display advertising along the side of a user's screen.

Facebook's stock rose 1.6% to $31.92 on Tuesday in 4 p.m. Nasdaq Stock Market trading. Its shares are down 16% from last month's $38 IPO price.

At Ford, Mr. Farley said the auto maker will spend more than 25% of its advertising budget on digital advertising this year, and the vast majority of that will be on interactive or social Web pages and not on banner ads. He said it's a mistake to equate interactions on Facebook with direct sales since the social site also improves Ford's image among buyers.

'This interaction and engagement [on Facebook] is something that you don't necessarily see in traditional media. That's why we continue to accelerate our digital advertising investment to more than 25% of our media dollars,' Mr. Farley said.

Ford pointed to the success of an app called the Mustang Customizer, which allows users to alter virtually a Mustang to their specifications, with the customized Mustangs competing for coolest design votes.

Ford said 4.3 million Mustangs were designed since the application launched last September, and that sales of Mustangs are up 18% this year. Ford thinks at least some of the sales increase is connected. But Mr. Farley said the customizer 'isn't about the Mustang, it's about building the Ford brand.'

Meanwhile, Coke is currently spending between 20% and 25% of its advertising budgets on digital and mobile platforms in some markets such as Japan, South Korea and Scandinavia, said Mr. Tripodi. 'Our mix is evolving and will continue to evolve,' he said.

Mr. Tripodi said he believes 'there needs to be some value' attributed to people who click 'like' on Facebook, or share advertisers' content on the site. He acknowledged that it may take 'a year or two' to come up with a more standard way to measure that value, similar to the way television charges for ads by the cost per 1,000 viewers.

Shayndi Raice / Mike Ramsey / Sam Schechner