---.htaccess----
<FilesMatch "\.(txt|json|html)$">
ExpiresActive On
ExpiresDefault A1
Header append Cache-Control must-revalidate
Header set Cache-Control "max-age=0, no-cache, no-store, must-revalidate"
Header set Pragma "no-cache"
</FilesMatch>

-----Request-----
Request URL:"ww.myzerver.com/myjson.txt"
Request Method:GET
Status Code:304 Not Modified
Request Headersview source
Cache-Control:max-age=0
Connection:keep-alive
If-Modified-Since:Fri, 03 Jan 2014 21:15:55 GMTSafari/537.36

-----Response-----
Response Headersview source
Cache-Control:max-age=604800
Connection:keep-alive
Date:Tue, 07 Jan 2014 03:42:10 GMT
Expires:Tue, 14 Jan 2014 03:42:10 GMT
Last-Modified:Fri, 03 Jan 2014 21:15:55 GMT
Server:nginx admin
X-Cache:HIT from Backend