Here's how Chromium handles this: http://www.chromium.org/chromium-os/chromiumos-design-docs/network-portal-detection
(link grabbed from one of the comments to the SO thread that Daniel posted)
Here's how Chromium handles this: http:// www.chromium. org/chromium- os/chromiumos- design- docs/network- portal- detection
(link grabbed from one of the comments to the SO thread that Daniel posted)