.dwt files not viewable in browser - why?

Hello;

I have created a .dwt file in Dreamweaver cc2015 but can not see it in browser localhost and have this error:

HTTP Error 404.3 - Not Found
The page you are requesting cannot be served because of the extension configuration. If the page is a script, add a handler. If the file should be downloaded, add a MIME map.

please let me know that how can solve it?

Thanks