When surfing via Firefox, you may sometimes encounter such a problem proxy server refusing connections Firefox is configured to use a proxy server that is refusing connection. Check the proxy settings to make sure that they are correct. Then Firefox rejects to connect to the Internet. Even though you have not made any proxy settings for your Firefox you may also get this error information. Perhaps you have started to get this annoying message everytime you try to use Firefox. This is because Firefox has somehow changed its proxy settings automatically, for example, maybe it has imported proxy settings from other browsers such as Internet Explorer or some others. So it's easy to fix, what you need to do is just modify the proxy settings of Firefox manually
Proxy Setting
1. Click Tools > Options
2. Click Network
3. Click Connection > Settings
4. Select No proxy
5. Click OK
Note: Upcoming version of Firefox browser may affect your settings.