How do I delete a network connection from my Air Port dropdown menu?

[Papillon]

This is a connection I did not set up. Is it possible some neighbor is using my airport to run their computer?

[struggle4progress]

1. Is it just recognizing available networks, or is it actually connecting to them?

[Papillon]

2. I don't know.

When I click on it, I get an AirPort screen that reads "The selected Airport network requires a password to join. And the Wireless Security reads "WPA Personal". How can I tell if it's connecting to the network?

Also, it doesn't always show up when I click on the AirPort icon.

[struggle4progress]

3. The message is telling you that you can't connect to the network without giving the WPA password,

which I assume you don't know and aren't trying to find out. The network doesn't always show up because the network isn't always available: its radio beacon isn't always on

I'd guess your mac is doing the right thing: scanning the airwaves for available networks, reporting what it finds, and asking whether you want to join detected networks

This isn't exactly what you need to worry about with wireless networks. You need to worry about the opposite situation: somebody else scanning the airwaves for available networks, finding your network, and joining it without your permission. The airport security default may be "None," so you ought to double check that and choose a secure password for your network if none is set

... By default, Wireless Security is set to None so that no password will be required to join the network. We recommend you click on the Wireless Security menu, select WPA2 Personal, and create a password between 8 and 63 characters long ... http://support.apple.com/kb/HT4259