As if Yahoo didn't have enough trouble already in social networking, a company employee tipped a New York Times reporter by mistake about a new, unannounced service called Yahoo Mash.

Recounting the faux pas in a New York Times blog Wednesday, Brad Stone reported that a Yahoo employee sent him an e-mail saying he had set up a profile for Stone in Yahoo Mash.

After Stone clicked on an e-mail link to visit the profile, he couldn't get past a log-in page. Yahoo representatives later acknowledged to Stone that the service isn't yet open to anyone outside of Yahoo and that the invitation was sent by mistake. They didn't provide him with more details about Yahoo Mash.

Asked for comment by IDG News Service, a Yahoo spokeswoman said that the service is at an "alpha" stage of testing in which only Yahoo employees are participating.

Considering that the service apparently includes the creation of profiles for individuals, it would be safe to assume it is some sort of social network, an area where Yahoo officials have acknowledged the company is weak.

TechCrunch, a technology news site that focuses on the Web 2.0 space, reported in July that Yahoo has been secretly working on a new social-networking project called Mosh.

What's not a secret is that the Yahoo 360 social network, introduced in March 2005, has been a disappointment. Several times over the past year, high-ranking Yahoo executives have publicly acknowledged this and indicated the service needs a major overhaul.

Yahoo 360 doesn't appear in a top 10 list of social-networking sites in the U.S. released Thursday by Nielsen/NetRatings. That list of the most popular social-networking sites with U.S. users during August, is topped by News Corp.'s MySpace with 60.3 million unique visitors.

Facebook, which Yahoo reportedly tried unsuccessfully to buy last year for $1 billion, came in second with 19.2 million unique visitors, a robust 117 percent increase over August of last year, outpacing MySpace's 23 percent growth clip.

Yahoo's weak position in social networking is baffling and has been a source of sharp criticism for the company's top managers. They have been blamed for being asleep at the wheel while MySpace, initially as a startup, went on a tear in the social-networking space; for launching a weak product; and also for being unable or unwilling to buy Facebook or another strong competitor.

Yahoo does have other, more successful social-media sites like social-bookmarking site Delicious, photo-sharing site Flickr, and question-and-answer search engine Yahoo Answers. However, it is generally agreed that it needs a strong contender in social networking, one of the hottest types of online services in recent years.

This story was corrected on September 13, 2007