My iphone 3gs won't connect to wi-fi?

My iphone 3gs worked on wi-fi then suddenly disconnected and when I search for a broadband it finds others but not mine, why? And yes I have the latest software on it, please help

Hold the power button and the home button down. When it restarts do not let go until you see the apple logo.

If it doesn't work go to settings and reset I think. Click reset network settings. This will not erase your phone

If that fails call your provider verizon att etc