In modern versions of Firefox some advances settings are moved to different locations in browser and are no longer accessible from main “Setting” menu. But that’s not going to be an issue if you carefully follow these following steps.
Step 1: Type “about:config” in the Firefox Address
First of all, type about:config in the address bar of Firefox. The same address bar where you put URL to open any website. Press the enter key after typing about:config. You do not need to put https:// or anything else like you put while entering address of any website.
Step 2: Click or Tap the “I accept the risk” button
This about:config can be used to mess up with settings of Firefox so you must have to be careful with it. Firefox will ask you for confirmation after you press enter key. Click or Tap the “I accept the risk” button there in order to go forward.
Step 4: Right click/tap on the “False” option