Firefox Proxy URL Configuration for Linux (Ubuntu)

In Firefox menu click Preferences in order to open the configuration page.
Select the Advanced icon in the advanced configuration window.
Then select the Network tab.
Then click Settings... in order to open the next window.
Select the Advanced icon in the advanced configuration window.
Then select the Network tab.
Then click Settings... in order to open the next window.
In the field named Proxy Configuration URL copy the following URL:

Please login to see the proxy URL.

Hint: Please enter the proxy URL correctly with no missing /extra characters. The proxy will work only if the Proxy URL is correct.
Click Ok to finish the configuration.