We check this website, now joomla51.com is up and dont blocked for our system and other users of the Internet.
So, answer to question: Is joomla51 Down Right Now? - NO! joomla51 is up!
If you have problem with access to site joomla51, and domain joomla51.com is not avalible.
Clear browser cache and/or try other web browser
(Chrome, Firefox or Safari).