In de Apache configuration there is a setting in wich you can set wich files should be returned as index when no file is specified.
There can me multiple files in there, something like this:
settings-name = index.html index.htm index.php
when no file is requested, apache will look for index.html, if it is not found it will look for index.htm and so on.
As Jay allready suggested, you should only place 1 index file in each folder. This to avoid problems when the setting is changed (without you knowing it).
You probably want to use index.html (for you're frame) and page.php (for the actual content?)
Greetz Daan