Q:

What's the WWW Server/1.1? 

I use netcraft.com query a site there shows Web server: WWW Server/1.1. 

I want to know what is it? 

A:

The WWW Server means that a web server is running, and the 1.1 is very likely shorthand for HTTP Version 1.1. 
In short, this result probably means that there was a web server found, and that web server is using HTTP Version 1.1.