"Free Public Wifi" is essentially a "viral" network. If you notice, it's an ad-hoc connection, meaning someone's computer is broadcasting that SSID. Google for it, and there was also a thread on this forum.

On your original topic, if you don't get the page, try going to the default gateway address (type route -n in a terminal, if it's not obvious what it is). This will often bring up the right page. In opera, you'd enter http://10.20.30.40, or whatever the gateway address is. Other options are <iprange>.1 or <iprange>.255