stack-popup-window-on-button-click
http://stackoverflow.com/questions/31956537/popup-window-on-button-click
HTML
<script src="https://netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<div id="login" runat="server">
<div class="modal fade bs-example-modal-sm" tabindex="-1" role="dialog" aria-labelledby="mySmallModalLabel">
<div class="modal-dialog modal-sm">
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal" aria-label="Close"><i class="fa fa-times-circle"></i>
</button>
<h4 class="modal-title" id="mySmallModalLabel">LOGIN</h4>
</div>
<a type="button" data-toggle="modal" data-target="#myModal">New User? Register Here</a>
</span>
</div>
</div>
</div>
<div class="form-group">
<div class="col-sm-offset-3 col-sm-9">
<asp:Button ID="BtnSubmit" runat="server" Text="SUBMIT" class="btn btn-primary pull-right" OnClientClick="javascript:return login();" />
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<!-- Login Popup -->
<input type='button' id='btn1' class='btn btn-default' value='login Popup 1'></button>
JavaScript
$('#btn1').click(function(){
$('.modal').modal('show');
});