If you want to hide your wordpress website, so that, only logged in users may access it. So, here’s the quick fix.

append following code into your wp-blog-header.php file right below wp();

//****************************************************//        
/////////////////////////// Require login to view website
get_currentuserinfo();
global $user_ID;
if ($user_ID == '')
{
        header('Location: wp-login.php');
}
////////////////////////// Require login to view website
//*****************************************************//

Thats it. Simple enough ?