One-stop resource on how to effectively disable SSLv3 in major web browsers as well as in web, mail and other servers that may still be using it.
Put the following line in your configuration file, or replace any existing line starting with ssl_protocols:
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
Then restart the server (in Ubuntu: sudo service nginx restart).
Don't forget to test your website.