Why is my wifi not working on the iPhone 4S?

The wifi is working fine. My iPhone 4S is connected and it works too, but, sometimes things just stop loading on the iPhone 4S. The software keeps giving me problems. I tried logging onto a laptop to see if there was something wrong with my wifi connection, but, the connection is just fine. The router is fine too. I've tried troubleshooting, etc., but, nothing is loading on the iPhone.