If you view this error on your homepage, this means that your domain has exceeded it's monthly bandwidth limit. Your domain bandwidth is made up of HTTP, SMTP, FTP and POP3 traffic.
To resolve this:
1.) You will need to upgrade to the next package ( which has a larger bandwidth ).
2.) Buy extra bandwith at 1GB bandwidth at N300/month.
3.) Wait till the end of the month, when the bandwidth will reset back to 0 for a new month.