Go to Settings (In the Menu bar click Firefox, select Preferences or Settings)
In the Privacy & Security panel, find the Website Advertising Preferences section.
Uncheck the box labeled Allow websites to perform privacy-preserving ad measurement.
Opting out:
Go to Settings (In the Menu bar click Firefox, select Preferences or Settings) In the Privacy & Security panel, find the Website Advertising Preferences section. Uncheck the box labeled Allow websites to perform privacy-preserving ad measurement.Software -> Firefox -> Uninstall.