When loading my domain in FireFox, I see "Did Not Connect: Potential Security Issue"

Symptoms

When loading your domain in the FireFox browser, you're presented with "Did Not Connect: Potential Security Issue".

Description 

This may be caused by an HSTS security policy and if your domain has an expired SSL certificate, you wont be able to connect to it with the FireFox web browser.

Workaround

1. Open the history window. Here's a shortcut to do it: ctrl + shift + h
2. Find the site you want to delete the HSTS settings for
3. Right click the site from the list and select "Forget About This Site"
4. Restart firefox