Go to the options page of the extension (usually located in your browser’s Extensions Manager) and disable the ‘Allow analytics’ option.
The Firefox Extensions Manager can be found at Firefox Menu > ‘Add-ons’ > ‘Extensions’.The Chrome Extensions Manager can be found at Google Chrome Menu > ‘More tools’ > ‘Extensions’.The Opera Extensions Manager can be found at Opera Menu > ‘Extensions’ > ‘Manage Extensions’.The Edge Extensions Manager can be found at Options Menu > ‘Extensions’ > ‘Netcraft Extension’ > ‘Remove’.