Freya comes with a captive portal assistant that tries to help you to login (accept ToS) on public networks (like Wifi in a café, etc.). When you connect to such network, a new window opens with what Freaya thinks is the portal website. Actually, it opens https://elementary.io/ and expects it to be redirected to the portal.
However useful it can be for most people, in some situations you may wish to disable this feature. It is very simple, but difficult to find out. Just run this command:
sudo chmod -x /etc/NetworkManager/dispatcher.d/90captive_portal_test
And that’s it!