Facebook is opening up its website so that member profiles can be found through online search engines such as Google and Yahoo!, as the social networking site looks to boost user numbers.

Starting today, Facebook will begin notifying members they have a choice over whether to keep their listings private or to allow Facebook to make their name and profile picture available when outsiders search the site.

The Palo Alto, California-based site has grown to 39 million members, up 62.5% from 24 million in late May.

Unlike most sites on the Web, Facebook has previously denied access by search services to information on the site.

But after notifying users over the next 30 days of its plans to open up basic profile listings of its members, Facebook plans to begin allowing sites like Google, Yahoo or others to crawl, or index, its public member profiles.

Early next month, non-members of Facebook will be able to type the names of friends or acquaintances into a search box on Facebook's home page to see if they have public profiles on Facebook in order to contact them.

But the move could still prove controversial among some members who prize the privacy protections Facebook offers relative to more open sites. Many members have criticised Facebook policy changes.