First check:

http://www.canyouseeme.org/

Type in port 80 from your server and make sure the outside world actually can see you through port 80.

Next, make sure apache is running. At the command prompt, typing <b>ps x | grep httpd</b> should return a line with "httpd" and a PID if apache is running. If it doesn't return anything, then apache is not running.

If both of those tests pass, but you still can't request pages from the outside, check your httpd.conf file and make sure apache is listening to the correct port/IP and the that your webroot has the correct file permissions.