When accessing the server via telnet, it gives out “HTTP / 1.1 400 Bad Request” What is the error?

Question

telnet

Hello !
1. In the OS command line I type "telnet phpwiki.ru 80" . A connection is established with phpwiki.ru
2. In the "telnet" utility (opened dialog box) I type the command "GET / HTTP/1.0" . I press ENTER.
3. "HTTP/1.1 400 Bad Request" is issued

Answer 1

telnet phpwiki.ru 80

GET / HTTP/1.1
Host: phpwiki.ru