// Create a refresh function:

    function refresh(){

        // SHOW overlay

        $('#overlay').show();

        // Retrieve data:

        $.ajax({

            url: 'data.html',

            type: 'GET',

            success: function(data){

                // onSuccess fill.container with response data:

                $('.container').html(data);

                // HIDE the overlay:

                $('#overlay').hide();

            }

        });

    }

    $(document).ready(function(){

        // Create overlay and append to body:

        $('<div id="overlay"/>').css({

            position: 'fixed',

            top: 0,

            left: 0,

            width: '100%',

            height: $(window).height() + 'px',

            opacity:0.4, 

            background: 'lightgray url(http://bradsknutson.com/wp-content/uploads/2013/04/page-loader.gif) no-repeat center'

        }).hide().appendTo('body');

        // Execute refresh with interval:

        setInterval(refresh, 1 * 1000);

    });