Whether you are using Safari or Firefox...
Firefox - If you are using firefox then when you have the browser open, go to the top where it says file, edit, view, ect. Click on the tab that says 'Tools' then click on 'Add-Ons'. There will be a screen that pops up and then you will click on the tab that says extensions. You will then have the power to uninstall webfetti.
Safari - If you are using safari then open the browser then go to view. After click on customize toolbar. You should then be able to uninstall webfetti.
Firefox - If you are using firefox then when you have the browser open, go to the top where it says file, edit, view, ect. Click on the tab that says 'Tools' then click on 'Add-Ons'. There will be a screen that pops up and then you will click on the tab that says extensions. You will then have the power to uninstall webfetti.
Safari - If you are using safari then open the browser then go to view. After click on customize toolbar. You should then be able to uninstall webfetti.