If you hadn't heard, from status.livejournal.com:
At 3:57 am EST on Thursday, February 20th, Admin lisa writes :Funny, I knew that was what had happened as soon as LJ stopped responding.
LiveJournal is currently under a Distributed Denial of Service attack, and has been since about 5:30pm PST (1:30 AM GMT) tonight. We have been working with our upstream providers (including several major backbones) to filter traffic as quickly and effectively as possible.
Due to the fact that a DDOS attack involves potentially tens of thousands of hosts all working together against a single target (in this case, us), it is extremely difficult to find one group of IP addresses to block to prevent the attack from affecting our services any further. Our upstream providers are currently filtering somewhere around 1/4 of the IPs on the internet from reaching LiveJournal. Unfortunately, these filters also block legitimate traffic from some users. When the attack has subsided we will remove the filters.
We will continue to monitor and block hosts as we gather more information regarding this attack. We seriously apologize for the inconvenience, and hope you understand we are doing everything in our power to get the site back functioning as normal.
Additionally, if you have any information as to who or what may be responsible for this attack, please email firstname.lastname@example.org.