You can now take a closer look at how to send information to the Web browser. These two blocks of information are separated by a blank line.
Browsers expect a header and the data from CGI programs, separated by a blank line.
The header is called an HTTP header. It provides important information about the information the browser is about to receive. It has become a fairly common way of expressing content type information. You can get more information on MIME from RFC1521. Some common MIME types.