Somewhere something happened.
I am not able to fix it.

error_page 404 404.html
During the test, i had this line in the site.conf file.

404.html had "File not found."

Later i created a proper error page and changed the commands like this.

error_page 404 404.php
But nginx is still throwing "File not found." but i have already deleted that 404.html file from server

When i check for error log, I am getting "FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream"

How do i fix it?