[Zope] extreme newbie questions

Hey folks, I'm a systems administrator at a university library in San Francisco, and about a week or so ago I set up a Zope installation for one of my users; he was able to become the administrator and start developing, but just yesterday he found that when he accessed the Zserver (let's say the Zserver runs on port 2323 -- when he goes to "http://machine:2323") he got the simple message "Not Found". Nothing else, no errors on the page, nada. I can't get anything either. He claims he didn't do anything yesterday that might have hosed the operation, but I'm at a loss -- I don't know enough about Zope to do an effective diagnoses. Any nudges or clues would be greatly appreciated. jf