By default your server will use index.html and / or index.php as the default index page of a directory. You can easily change the directory index by adding the following code snippet to your .htaccess file.
In this code snippet I have used home.html as the new default index page. You can change it to whatever you want, i.e. whatever.html.
You can also have multiple directory index pages, like this:
DirectoryIndex index.php index.html home.html