Hello I Have an Iphone 4s, and my Wi-Fi has "greyed-out"....I don't know how to fix it

What steps from http://support.apple.com/kb/TS1559 have you tried already?

Hai, I too had the same problem. It came only after i updated my phone to IOS7. It was good for two weeks and suddenly the wi-fi greyed out. As my phone s not covered under warranty i sarched net to find a solution. did basics like Resetting network settings, restoring phone and everything thats on the blogs. A weired method gave my wi-fi back. As my phone is not under warranty i went for a toss. Initially i turnrd off my phone and left in fridge for ten minuts and then switched it on. My wi-fi was on for 1 hour and again it went grey. Control centre indicates wi-fi is on but the switch is turned off. I did again reset the network settings and switched off the phone. Now i opened the back case and heated the phone(at area where wifi chip is present) with help of hair drier for two minuts. i allowed it to cool for 30 mints and then switched it on again. To my surprise my wi-fi is back. I dont know if i can suggest this crude method to u but if u are out of warranty there is nothing to loose. Will update in case if it fails or continues to work. Hope this info will help some folks.

Hey, that's incredible but it works. I have the same failure, and I've turned off the mobile phone and cooled it. That's probably is a problem with solder (on wi-fi component).

My mobile now is out of warrenty (to change it I've to pay 199 euro), so... My mobile will work without wi-fi.

What I suggest is (that is what I've observed) :

the software doesn't detect the failure and disable the wi-fi ... but simply greyed out the possibility to switch on/off the wi-fi (and probably it is switched on) .. the mobile phone in this state has a battery decrese very high and it warms a lot.

So when I have had the possibility (when I was colled and the wi-fi work) I've disabled the wi-fi ..I'll use it just for a few time when I've to do software upgrade before the high temperature of the component will greyed out again the wi-fi.