Browsers - Bypassing HSTS Warnings

Sometimes the browser will show an HSTS warning message

Some browsers use HSTS (HTTP Strict Transport Security), which lets a web app remember that it should only be accessed over HTTPS. When this happens, the fix is to clear the browser cache. Open the Privacy settings in Firefox and clear your recent history: Now the Cache and Active Log-ins with a Time range to clear set to Everything and Click Clear now.

As a last resort, you can fully disable HSTS in Firefox:

Type about:config in the Firefox address bar. A warning may appear; click OK.

In the list of preferences, look for network.stricttransportsecurity.preloadlist, right-click it, and toggle it to false.

If the preference is not in the list, right-click anywhere on the page, select New > Boolean, name it network.stricttransportsecurity.preloadlist, and set it to false.