"Facebook has thrown the switch on a system that lets users browse other sites via the networking portal. Called Connect, the system lets Facebook members use their login credentials to access other websites.

The system also gives feedback about what a Facebooker's friends have been doing on those partner sites. Among the first sites visitable through Connect will be the Discovery Channel, social news site Digg, as well as video site Hulu.

Connect was first announced in May 2008 and is Facebook's response to the work of rivals, such as MySpace, who have rolled out similar systems.

All the sites are keen to ensure that they do not become a place that members go but are the only place they have to go as they can use their login information to get at content anywhere else.

Behind the initiatives are software projects that open up the basic interfaces for the social sites, so others can understand how they format data about members' activities.

The built-in socialising tools on sites such as MySpace and Facebook will mean that friends can virtually gather, for instance, to watch a video via Hulu and chat about it all in the same place.

By making a social site an all-encompassing portal, the hope is that they will become more attractive to advertisers.

Facebook said it would vet all those sites that wanted to sign up to Connect and review what they will do with data gathered about members. In this way it hopes to avoid the bad PR it received for a prior programme known as Beacon.

That shared information widely about what Facebookers did with their time and won criticism because it did not seek permission before sharing data which was sometimes very personal. "