Placing the web server in a separate Demilitarized Zone (DMZ) behind the firewall is a security best practice that allows an organization to isolate its public-facing services from the internal network. This setup ensures that if the web server is compromised, the attacker would not have direct access to the internal network resources. Additionally, the DMZ provides a controlled environment where network traffic to and from the web server can be monitored effectively, facilitating the detection of any future attacks. The firewall serves as a barrier, with specific rules that only allow necessary communication to and from the DMZ, thereby enhancing the overall security posture of the organization.