Firefox 16+?
Do you want Firefox 16 or will Firefox 16 and up (17, 18, 19, etc) do? You're running 28 at the moment. Plus your profession shouldn't have that low of a version of Firefox. 16 isn't even supported anymore and is WAY out of date.

What problems are you having with Firefox that prevent the current version from working properly?

When Norton removes a file, it should be found in Norton's Quarantine area.

Where did you try to download Firefox 16.0 from? There are a number of sources that offer older versions of software that "package" unrelated applications in their own installer executable. IOW, you get a "surprise" when you go to install that download; extra garbage that you aren't expecting to be installed with Firefox. Maybe Norton is seeing those extras and disallowing the download, because it ain't just Firefox that you are trying to download?

Compatibility and/or security issues.
http://www.mozilla.org/en-US/firefox/16.0/releasenotes/
First offered to release channel users on October 9, 2012

Whereas Windows 8 was released for general availability on October 26, 2012. I can only guess that Firefox 16 isn't as compatible with Win8 as later versions of Firefox were.

Plus as Moses alluded to, Firefox 16 is missing hundreds of Bug fixes that are present in Firefox 28, and is lacking some important security patches. So, if you're going to use Firefox 16 don't use it on the internet, use the current version instead for web surfing and use Firefox 16 for a local intranet only.