Use Curl and see what that says, ea:
curl -i www.site.nl/robots.txt
HTTP/1.1 200 OK
Server: nginx/1.9.13
Date: Wed, 06 Apr 2016 05:52:43 GMT
Content-Type: text/plain
Content-Length: 72
Last-Modified: Sun, 16 Oct 2011 19:52:44 GMT
Connection: keep-alive
ETag: "4e9b360c-48"
Accept-Ranges: bytes
curl -i www.site.nl/robots.txt
HTTP/1.1 200 OK
Server: nginx/1.9.13
Date: Wed, 06 Apr 2016 05:52:43 GMT
Content-Type: text/plain
Content-Length: 72
Last-Modified: Sun, 16 Oct 2011 19:52:44 GMT
Connection: keep-alive
ETag: "4e9b360c-48"
Accept-Ranges: bytes