In Firefox 56+ the "Warn me when web sites try to redirect or reload the page" setting can no longer be found in Options/Preferences.

You can modify this pref on the about:config page to enable or disable this feature

• http://kb.mozillazine.org/accessibility.blockautorefresh

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• http://kb.mozillazine.org/about:config

Thanks cor-el. I eventually found out that by hitting the correct side of the mouse I could toggle the preference from modified to default.

This answer does not explain how to turn this annoying new feature off.

"Warn me when web sites try to redirect or reload the page" can only be enabled in current Firefox releases by setting the accessibility.blockautorefresh pref to true on the about:config page or when you have modified this in an older Firefox version in "Options/Preferences -> Advanced".

In Firefox 56+ this choice was removed from Options because of the redesign of the Options page (about:preferences) and you need to modify the pref directly on the about:config page.

• https://support.mozilla.org/en-US/kb/firefox-options-preferences-and-settings