How to determine is a web server use which type of OS

[ivanovic]

Is there any way to determine which type of OS is used on a web server
by looking the contents on the page address in a websites or by other ways.

[cgrantski]

Yes. Get any of the page-header viewing tools like Fiddler or HTTPWatch, browse to the site in question, and examine the Header info. It'll be listed.

[phranque]

the Server header that is returned will tell you something about the web server software but not exactly the operating system.
if it's an IIS server you can assume it's window-based.
that's about it...

[cgrantski]

Oops, assumed that was the question.

Try googling the NetCraft site and go to its Uptime window.