403 error with codeignitor

When I type in the standard web address for my site, I get a 403 error. However, when I type in a more exact address, say pointing to an index.php file, everything shows up fine.

I'm using Anodyne Productions' Nova (SMS 3) which uses codeignitor. All accompanying software (PHP/MySQL) is compatible.

I'm not a very technical person, so I'm hoping that this is an easy fix.

Thanks for taking the time to answer.

Thanks for the tip. I ultimately dealt with the issue by setting up a redirect in CPanel.