I want to stop yahoo e-mail from poping up ,in right lower corner of the screen

https://support.mozilla.org/en-US/kb/push-notifications-firefox https://support.mozilla.org/en-US/kb/push-notifications-firefox#w_how-do-i-revoke-web-push-permissions-for-a-specific-site If these are as small popups on bottom right corner of Firefox windows then this may be web push notifications from sites you have allowed to send you notifications. You can revoke these sites in sending you notifications.