This error indicates that you have been disconnected from the megaserver.

• Check the Service Alerts page to see if ESO is experiencing an outage or going through maintenance.
  • If ESO is experiencing and outage or undergoing maintenance, you will have to wait until the servers are restored to log in.
• If you attempt to log back in right away, you will receive an Error 304. We recommend waiting for a period of 15-20 minutes before attempting to log in again.
  • The reason to wait the 15-20 minutes is that the server needs that time to "catch up" to your data. If you log back in before the server has updated your account appropriately, the server will think you are still online and your character will be booted again.