This problem is likely due to a misconfiguration in the directory index directive.

In your Apache configuration file (/etc/httpd/conf/httpd.conf) the DirectoryIndex directive gives the web server a list of files to look for if you do not specifically reference a file name. The first file in the list that exists will be loaded. The default DirectoryIndex directive is:

DirectoryIndex index.html index.shtml index.html.var index.php

If your index file is index.htm, it is not listed in this directive and will not be displayed.

You can resolve this issue two ways: Either add "index.htm" to the DirectoryIndex command (then restart the web server) or change the name of your index.htm file to index.html.