From what I understand you want to do this in Django. Well, if in your case you want to make a registration and after the registration display the message, my tip would be this:
And at the end of the registration function of your view you should add a render request, like this:
def nome_da_sua_view(request):
# Código de cadastro aqui
return render(request, 'thanks.html', {})
Remember that it should stay within the validation if it is a POST method, something like this:
if request.method == 'POST':
Then you should add this redirect to your URLs:
urlpatterns = [
url(r'^thanks/', 'nome_do_seu_app.views.nome_da_sua_view'),
]
Finally, inside your template folder, it should contain an HTML file called thanks.html.