I wanted to add a user to have permission to login to our webserver. Foolishly I did not back this file up. The only thing I changed was the last part of the file which was:

# override default of no subsystems
AllowUsers chris acosentino
Subsystem sftp /usr/libexec/openssh/sftp-server

to

# override default of no subsystems
AllowUsers acosentino techmaster
Subsystem sftp /usr/libexec/openssh/sftp-server

Now I'm still connected with that terminal, but any other attempt to get into the webserver from either a new terminal or from winscp results in:

ssh_exchange_identification: Connection closed by remote host

Please advise me as to what to do. If I lose connection to this last terminal I guess I'll be screwed.