In order to connect to your Mac, it needs to be awake or able to be woken up.
If your Mac is connected using EasyConnect you cannot let your it go to sleep, even if you have a compatible Airport device. Use Energy Saver in System Preferences to stop your Mac going to sleep, otherwise you won't be able to connect to it.
The menu bar icon will be blue if you're connected with EasyConnect, or you can check in the Connection pane.
You can use this option if you have Snow Leopard.
Now it should be safe to let your Mac go to sleep. When you connect to Webjimbo, your Mac should wake up. Make sure you test it from another computer on your network if you can. If you have trouble, there's lots more information in this Macworld article.
If you have a newish Mac (2009 onwards, perhaps), the above should work on a wireless connection too. If your Mac supports this, the option described above will be called "Wake for network access". Again, the Macworld article has useful information.
If you don't have an Airport base station, or if the above doesn't work for you, your options are: