On Windows 7 and later, the system will automatically detect network connectivity and alert user if there's no internet access. I've spent some time on learning how this works, and here is the technical detail: <a href="http://blog.superuser.com/2011/05/16/windows-7-network-awareness/" rel="nofollow">http://blog.superuser.com/2011/05/16/windows-7-network-aware...</a><p>I wonder why OS X doesn't have such a useful functionality...