if(JFactory::getUser()->guest) {
    echo '
    <div id="ModalStart" class="modal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
        <div class="modal-header">
            <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
        </div>
        <div class="modal-body">
            <h4>You are not logged in </h4><br>
        </div>
    </div>
    ';
    }