"Unable to connect to the proxy server" after updrade to Android 4.3 My Samsung S4 has been experiencing the problem of "Unable to connect to the proxy server" after upgrade to Android 4.3, all the apps need network (HTTP) are not working, no matter 
using 4G or Wifi connection. For apps which does not require HTTP connection such as Whatsapp or Google Search which is ok.

I have double checked the Proxy setting in my Wifi Setting, which is set to none, so are there anything I have missed or misconfigured?
Tap and hold the WiFi button, then select "Forget Network". Afterwards, search for the network again in the list, enter the password and you are good to go.