You haven't given much to go on, but try this in your root directory (/) and named index.php:
<?php
echo "hello world\n";
?>
At the least, your browser will say Hello to you when you access your site. From there you can add more stuff to make it a proper HTML page. You can give your scripts other names and paths and access specific scripts in specific places within your site from the browser address bar.
If the above does not work, trying giving that path and name (/index.php) explicitly on your browser. If it then works, you have something wrong in your .htaccess file (it's not looking for an index.php file).
