If you see your website offline, but it is online if visited from another connection (from example from your 3g smartphone connection) most likely your IP address has been blocked.
To protect our client's accounts our servers have a firewall.
Once a given Ip address tries to access to services (like cpanel, email using a client, webmail, FTP) o for other suspect actions our server blocks the IP address (temporary or permanently).
In 99% of the cases a client's IP is blocked for failed login attempts. If you believe your IP has been blocked you should contact our support giving us you IP address. You can retrieve it going to ip.supporthost.net.
We offer up to 5 free unblocks a year per account, the next will cost 2€ each if the client keep trying to login with wrong login data. We usually do not enforce this unless we happen to unblock the same IP over and over.