on the webassist/plugins/registration/registration.php page, you could edit line 141:
php:
header("Location: ".((isset($_GET["accesscheck"]))?$_GET["accesscheck"]:"users_profile.php") ."");
to pass a querystring variable:
php:
header("Location: ".((isset($_GET["accesscheck"]))?$_GET["accesscheck"]:"users_profile.php?reg=1") ."");
then edit the users_Profile.php page to show a thank you message:
php:
<h1><?php if(isset($_GET['reg']) && $_GET['reg'] == 1) echo("Thank you for registering<br />"); ?>Profile</h1>
