1) http://www.downforeveryoneorjustme.com/ - down for everyone? Or is it only affecting you?
2) if its up for everyone and only seems down for you, most likely your IP has been blocked by the firewall.
3) go to http://whatismyip.com and take note of your IP address, please include this in your support ticket so we can unblock quickly.
4) if your website is down for everyone, do a tracert by domain name and IP
On windows hit "start" then "run" type cmd
then at the command prompt type tracert yourdomain.com
select all and copy the results (use the tool at the top left of the prompt window)
5) Then go to the "Customer Area" and open a support ticket including the tracert results (paste). Also include your IP address so we can remove it from the firewall block list if that is the case.