Use bootstrap cards for feedback pages

Change-Id: I811bf2f3ce2992b7110d6742069eb07f38bd5b37
diff --git a/templates/registration_limit.htm b/templates/registration_limit.htm
index e8a67dd..5e48abc 100644
--- a/templates/registration_limit.htm
+++ b/templates/registration_limit.htm
@@ -1 +1,3 @@
-<h2>Sorry but you already registered!</h2>
+<div class="alert alert-danger" role="alert">
+    Sorry but you already registered!
+</div>
\ No newline at end of file