The Norton Toolbar is now compatible with Firefox 17. We have released a Firefox 17 compatibility patch for Norton Internet Security & Norton 360 20.2.0.19 which is available via LiveUpdate. If you are not seeing the Norton Toolbar in Firefox 17, check and make sure you're running NIS or N360 20.2.0.19. Please visit our Norton Update Center to receive the latest update.
http://community.norton.com/t5/Norton-Toolbar-Norton-Identity/Firefox-17-Support-for-Norton-Toolbar/td-p/853416

Norton firefox https://www-secure.symantec.com/norton-support/jsp/help-solutions.jsp?ct=us&lg=en&product=home&pvid=f-home&version=1&docid=kb20100122090203EN_EndUserProfile_en_us

If you installed Norton via Comcast then you may have to update that software via the Comcast website and can't do this via the Norton website.

See also:

• http://forums.comcast.com/t5/Security-and-Anti-Virus/bd-p/13

You can't download Norton Toolbar independently either you can update your Norton product! Here's a KB article which will help you to fix this issue - https://support.norton.com/sp/en/us/home/current/solutions/v58055475_EndUserProfile_en_us