Firefox 4'''2'''.0 is old now and [https://www.mozilla.org/en-US/firefox/releases/ Firefox 4'''4'''.0.2] is the current. It is Norton that has to update their toolbar extension for major Firefox Releases, not the other way. http://community.norton.com/en/forums/norton-toolbar-limited-compatibility-patch-firefox-44-available https://community.norton.com/en/blogs/product-update-announcements/norton-toolbar-limited-compatibility-patch-firefox-44-available The Firefox web browser is not made to be compatible with the hundreds of Extensions and its versions out there. Firefox Releases would take forever if it was.