I think that is a default away message. Depending on the client you use, you may never be asked to supply a message. For example, here at work using ICQ2Go, I don't get to choose my away message, and I infact have no clue what it uses for my away message. On the other hand, I seem to recall that with ICQ pro 2001a, I would be prompted with the option to change my message whenever I selected a non-available status.