An SSID is the name of your Wireless Network. For example, it could be NETGEAR or JohnsHouse or almost anything. Usually your SSID is visible, but wireless routers have the option to make it invisible, in which case you will need to type it out.

Normally, Firefox wouldn't ask for the SSID because your wi-fi connection is managed by your device's network settings. It sounds a little suspicious to me.

I am with virgin mobile

Hope this answers your question.

Go to: http://www.virginmobileusa.com/resources/mifi_usermanual.pdf

Please go through page 8 and page 14.