Consultation: http configuration problems

For more information about http configuration, see Linux general technology-Linux technology and application. Today I configure http, and finally
Service httpd restart
Stopping httpd: [OK]
Starting httpd: [OK]
But I enter the http://www.example.com in a browser
But it does not show my webpage. The output is You have reached this web page by typing "example.com", "example.net", or "example.org" into your web browser.
These domain names are reserved for use in documentation and are not available for registration.

The httpd. conf configuration is as follows:
NameVirtualHost 192.168.100.101

ServerName www.example.com
ServerAdmin ywhqiuyun.yuer@www.example.com
DocumentRoot/var/www/virtual/www.example.com/html
ErrorLog logs/www.example.com-error_log
CustomLog logs/www.example.com-access_log combined

Options Indexes Includes




Excuse me: Why?