var sidebar_align = 'right';
var content_container_margin = parseInt('350px');
var sidebar_width = parseInt('330px');
How does netcraft detect OS?
I understand Apache leaks the name of server via ServerToken. But I can not find a way how netcraft detect the OS which the server is running on. From ping maybe?
Typically using packet fingerprinting. There are plenty of programs that can do the same for you if you want to find out info about some host, for instance "nmap".
Keep in mind that you shouldn't mess around with scanning hosts you dont have permission to mess around with!
Depending on OS and webserver configuration, the webserver may also post the OS information right in it's version string/token.