Since this is a login div, shouldn't the default be to NOT display it. I am going to go ahead and assume then you want to display it then via javascript.
<div id="login" style="display:none;">Content</div>
Then using jQuery:
<script type="javascript">$('#login').show();</script>
Another method you might consider is something like this:
<div id="login" style="display:<%=SetDisplay() %>">Content</div>
And the SetDisplay() method output "none" or "block"