It means that the computer cannot connect to the printer you're directing it to. This could mean that the printer is powered off, but you'd probably have noticed that.
If that's not the case, it means there's a problem with the connection between your computer and the printer. Check all your cables/connection stuff, and then check the list of printers and see if there are two with the same name. That's what happened to me, once, when I plugged the printer into the computer directly. It created a second printer called (printer name)-1, and I have to make sure I select the right one to print properly.