I have a SIM-lock free Galaxy W with Android 2.3.6 on it.
The other day in the public library I found out that I was not able to login anyhow to the public Wi-Fi.
It shows that the DHCP gives the phone an IP address and then labels it as connected, but on the PC a "further data needed" kind of notification would appear in order for me to put username and password in.
Now I found the "Free Wi-Fi hotspot" that deals exactly with this and am going to test it today, but it looks just like a frontend. Really there is not a way to access them using only built-in options on Android?
EDIT: Trying opening my browser after connecting doesn't automatically redirect me anywhere. That's why I avoided using the term "captive portal" as I cannot see any portal.