My wifi won't turn on, on my 4s.

Is Wi-Fi grayed out?

Have you tried restarting the iPhone?

This might help ya out -> iOS: Wi-Fi or Bluetooth settings grayed out or dim

Did you sort it? i have the same problem

I had this same problem on my iPhone 4S this morning. Mine stopped working after I had to do force my phone to reboot last night as it wouldnt turn on. I just went into Settings --> General --> Reset --> Reset Network Settings.

You'll have to re-enter your wifi password, if you have one, but you should be able to use wifi once you do this. It worked right away for me.

Hope this helps.

i have already reset my network seting and it worked for an hour then stoped so i tried a couple more times and still nothing so i rest the phone to factory setings and now there is ios7.0.2 and i cant download it without wifi please help

Had the same problem and did the following to resolve the problem.

Go to settings and turn on Airplane and leave WiFi off go back to the home page then go back into settings turn off airplane and turn on WiFi. See if that works for you.