There are three general classes of error messages you might see when you use Internet services. Although the text of the error message might vary from one application to the next, they are generally similar, and you should be able to recognize the problem from the message.
The first type of error occurs when you try to make a connection. The message typically says ``unknown host'' and includes the name of the host you are trying to connect to. First double-check the spelling of the host name and domains to make sure you didn't type them wrong. If you have the name correct, there are two other reasons you might not be able to make a connection. The host name might not be known to the name server your system used, or the host might not exist. In the former case you might try again, but use the numeric Internet address if you know it.