See, I have my Steampapps folder stored on my extenal drive, and don't have internet on my main PC, so, I use a laptop(connected to external) to update my CSS. Try to go to offline mode, follow all directions. And, I guess, it would work quite fine, on my laptop at least.
Plug in my external back to my main PC, I try CSS(offline), and get approximately the following error: "Unable to connect to the steam network. 'Offline mode' is unavailable because there is no Steam login information stored on this computer.
You will not be able to use Steam until you can connect to the Steam network again."
Any advice, friends???