Unable to browse any domain hosted on the Plesk server. The browser displays this error:
502 Bad Gateway
The Apache service is stopped on the server.
Since Plesk 11.0, Nginx can be installed as a reverse proxy server in front of Apache. The Nginx process runs on ports 80 and 443. It accepts all HTTP(s) requests and forwards them to Apache, which runs on 7080 and 7081 ports.
Check the Administrator's Guide for more details about Nginx.
If the browser returns the error
502 Bad Gateway, make sure that the Apache service is running on the server:
# service httpd start //RedHat based
# service apache2 start //Debian based
The status of the Apache service can be also checked from the Plesk: Tools & Settings > Services Management