Facebook crash - 'worst in four years'

Social network giant Facebook has said its crash on Thursday was the worst in four years. Around 135 million people were affected when the site went down at 1900 BST.

It was around two-and-a-half hours before the site was back up and running again. The site, which has 550 million users worldwide, blamed a software flaw which caused huge disruption causing engineers to work on the site and shut it down whilst they did so.

The downtime would have been peak for users in the UK and Europe.

On other social network sites such Twitter, millions of users were posting blogs and comments about the Facebook's shutdown. One of Facebook's senior engineers Robert Johnson apologised on his blog:

" The key flaw that caused this outage to be so severe was an unfortunate handling of an error condition. An automated system [to fix the problem] ended up causing more damage than it fixed. Once the database had recovered and the root cause had been fixed, we slowly allowed more people back onto the site. "

Most people who tried to log on were greeted with a network error message "Network Error (dns_server_failure)"