There is a popup blocker available on the browser use the web to find out how to set it.
If the above doesn’t stop it can you repost with your operating system the mane of the browser you are having the pop up on and the version of that browser?
Is the pop up happening on more than one browser?
What is the name of your Norton product and the version number, you can find this by clicking the Norton icon, click support, hover over, about, on the window that opens, the second line down is the version number.
Can you post an image of the pop up using screen capture and the paint programme or use the snipping tool (see help and support from the start menu).
How to post an image in the Norton forum, link below. Please check that personal information is edited out this can be done using the paint programme see help and support from the start menu.
What browser are you using?
You probably need to change a browser setting for updates, to disable notifications.