For example:
athena% telnet -u www.mit.edu 80
Trying 18.181.0.31...
Connected to DANDELION-PATCH.MIT.EDU.
Escape character is '^]'.
GET / HTTP/1.0
HTTP/1.1 200 OK
Date: Fri, 20 Feb 1998 22:45:44 GMT
Server: Apache/1.2.5-dev
Last-Modified: Fri, 20 Feb 1998 18:55:16 GMT
ETag: "431a-b83-34edd194"
Content-Length: 2947
Accept-Ranges: bytes
Connection: close
Content-Type: text/html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2
Final//EN">
<html>
<head>
<title>MIT SIPB Home Page</title>
[...]
</div></body>
</html>
Connection closed by foreign host.
An example of the browser using a parameter is in loading cached pages, where the browser reports how old its version of the page is, and the content is only sent if the page has been modified since then. Here's an example of a successfully cached page:
athena% telnet -u www.mit.edu 80
Trying 18.181.0.31...
Connected to DANDELION-PATCH.MIT.EDU.
Escape character is '^]'.
GET / HTTP/1.0
If-Modified-Since: Fri, 20 Feb 1998 20:00:00 GMT
HTTP/1.1 304 Not Modified
Date: Fri, 20 Feb 1998 23:01:53 GMT
Server: Apache/1.2.5-dev
Connection: close
ETag: "431a-b83-34edd194"
Connection closed by foreign host.