Solution:
For this you need to redirect login/registration page to your custom pages. So, Write this code in your functions.php
file Under your activated theme folder. Pass your custom page path as a Argument.
add_action('init','possibly_redirect');
function possibly_redirect(){
global $pagenow;
if( 'wp-login.php' == $pagenow ) {
wp_redirect('http://google.com/');
exit();
}
}