app/views/shared/_flash.html.erb
<div class="alert_banner">
<div class="alert_msg error_msg" id='error_msg'>
<%= flash[:error] if flash[:error] %>
</div>
<div class="alert_msg notice_msg" id='notice_msg'>
<%= flash[:notice] if flash[:notice] %>
</div>
</div>
<script type="text/javascript">
$(document).ready(function() {
if ($('#notice_msg').text().trim() != '') {
$('#notice_msg').fadeIn(300);
$('#notice_msg').delay(3000).fadeOut(300);
};
if ($('#error_msg').text().trim() != '') {
$('#error_msg').fadeIn(300);
$('#error_msg').delay(3000).fadeOut(300);
};
});
</script>