Ipod Touch 3rd gen Wifi Connection Question

Hello, I'm using the touch while I work around NYC. I can connect to a bunch of open wifi connections, but many of them don't connect me online.

What happens is I'll find an open connection and successfully connect to it with usually a very strong signal. It'll show up on the top right as connected. However, when I try to go on the app store it'll say "Invalid Argument" and when I try to use safari, the screen dims a bit and just says "Connecting" at the middle and just stays like that.

I was wondering if anyone could tell me what the problem is with these wifi connections.

Just because it says "connected" doesn't mean you are connected to the internet, it can mean you are connected to the router or device sending out the signal to connect to it. You can have a router that has a password connected to another router that isn't password protected, which will let you in and connect to the router, but not the internet.