HTML
<!-- Modal -->
<div class="modal fade" id="myModal" role="dialog">
<div class="modal-dialog">
<!-- Modal content-->
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal">×</button>
<h4 class="modal-title">Modal Header</h4>
</div>
<div class="modal-body">
<p>Some text in the modal.</p>
</div>
<div class="modal-footer">
<button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
</div>
</div>
</div>
</div>
JAVASCRIPT
<script>
$(document).ready(function(){
$("#myModal").modal('show');
});
</script>