Norton thinks there is something bad in the prefs.js file. It could be a web link or coding.

It would be best to remove that file and redo your settings. Keep track of what you are doing in case the error returns.

Note that prefs.js is a text file despite its .js file extension that stores settings like you make in Settings (Options/Preferences) that aren't default, so there is usually no need to suspect this file. If Norton doesn't give detail about what specific content it finds suspicious then all you can do is contact Norton for support.