Editable message after registeration is there a way to make this message controllable from back end which appear after user registration.

   $message = t("Thank you for registering at $site_name. Your application for an account is currently pending approval.&lt;br/&gt; Once it has been approved, you will receive another e-mail containing information about how to log in, set your password, and other details.");


because it contains HTML it can't be done by string override.
Anything inside a t() function can be overridden, you need to paste the exact contents into String overrides in settings.php or use the String Overrides module