The Server response-header field contains information about the software used by the origin server to handle the request. The field can contain multiple product tokens (Section 3.7) and comments identifying the server and any significant subproducts. By convention, the product tokens are listed in order of their significance for identifying the application.
Server = "Server" ":" 1*( product | comment )
Server: CERN/3.0 libwww/2.17
If the response is being forwarded through a proxy, the proxy application must not add its data to the product list.
Note: Some existing servers fail to restrict themselves to the product token syntax within the Server field.