My iphone wont let me turn on wifi?

I have an iphone 4s and i cant turn on my wifi, when i go on the wifi tab it is just grey and i cant select it to turn it on. How do i fix this? Please help!

Added (1). I tried reseting the network but it still didnt work, please does anyone know how to fix this?

Is airplane mode on? Turn off factime? Uninstall skype and reinstall skype(if its installed)? Try resetting your network settings? If all these fail please call Apple and setup a time to meet someone at the apple genius bar for repair or replacement. Be aware there are costs to this if you did not purchase applecare+.

Thank you… Works great now!

DONT TRY IT ITS NOT GONNA WORK