If you locked yourself out of SSH in WHM/Cpanel for whatever reason--e.g. you specified an invalid AllowUsers in /etc/ssh/sshd_config--you can reload SSH service in safemode, by pasting this into your browser's address bar:
Then login with your root credentials, and sshd will be restarted in safemode, allowing you to login and fix your /etc/ssh/sshd_config.
Once done, restart ssh:
service sshd restart