Scenario: If you access a url with a trailing slash it causes the port number of nginx to be appended to the URL and in most cases either breaks the page or causes a blank page.
To fix this you need to configure nginx to prevent adding the port number when a redirection is caused by a trailing slash.
Add the following in your nginx.conf at /etc/nginx/
Restart nginx and subsequently varnish.
Credits: CNST (http://serverfault.com/questions/351212/nginx-redirects-to-port-8080-when-accessing-url-without-slash)