It's saying that "dressed" (without the quotation marks) is an unknown command. I've never seen "dressed" as a valid command on any network. Additionally, it tells you how you can get further assistance.
Try /msg InfoServ HELP for more information
As this is a problem with that specific network, your first line of clarification should be using the HELP command (as indicated above),
If that is insufficient, then you should refer to the networks help channel, usually #help.