A web server is a program that responds to network requests over the HTTP or HTTPS protocol.
A web server is a program that responds to network requests over the http or https protocol.
Use this tag for questions about web servers in general. For questions about a specific web server application, use the application-specific tag instead: apache-httpd (Apache 1.x or 2.x), openbsd-httpd (OpenBSD's fork of Apache), lighttpd, nginx, …
Do not use this tag merely because the computer in the question happens to be a web server, only if serving web content is directly relevant to the question.