Yesterday Cornelius committed to the needed pieces to detect online/offline events. These events seem to be supported by Firefox 3.0+ and Internet Explorer 8 currently only, but are part of the upcoming
HTML 5 standard. This means that any modern browser will support them in the future.
These events are of great use for us. Currently we use these events only to display the current status in the lower right corner. In the future we can start building features upon these event. For example we can start synchronizing data stored offline back to the Tine 2.0 server. Or we can start updating the offline cache. And many more.
Using Kubuntu Hardy you can enable and disable your network connection and see the connection status toggle between online and offline. Unfortunately it does not work with Firefox on Cornelius Mac. Maybe someone can test how it works on Windows.