Apache - Firefox Can't Establish a Connection to the Server at Localhost

Im not able to access my localhost server by firefox. Im using apache, and ive tried to run the following commands

$ service apache2 status

 * apache2 is running

$ sudo service apache2 restart

 * Restarting web server apache2                                         [ OK ]

$ sudo netstat -nlp | grep apache

tcp6       0      0 :::81                   :::*                    LISTEN  
2658/apache2    

any help?

firefox displays this error message:

"Unable to connect

Firefox can't establish a connection to the server at localhost.

    The site could be temporarily unavailable or too busy. Try again in a few moments.
    If you are unable to load any pages, check your computer's network connection.
    If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web."