Message box

What's a message box ?

do you mean in JavaScript?

You may be interested in the RedBox library.

http://www.agilewebdevelopment.com/plugins/redbox

-NSHB

Just do:

<% unless flash[:error].blank? %>
<script>alert(<%= flash[:error] -%>)</script>
<% end %>

And in your controller :

unless login_successful?
flash[:error] = 'Login unsuccessful.'
end