Jquery Ajax loading image while getting the data
<script type="text/javascript">
    jQuery(function($) {
        $(document).ready(function() {
            $("#imgs").hide();
            $(".letter").bind('click', function(){
                $("#imgs").fadeIn();
                var val = $(".letter").val;
                var site = '<?php echo site_url(); ?>';
                $.ajax({
                    url: site+'/wp-content/themes/premiumnews/newContent.php?letter='+$(this).html(),
                    success:function(data){
                        $("#imgs").hide();
                        $("#content1").html(data);
                    }
                });
            });
        });
    });
</script>

$('#loading_div').hide().ajaxStart(function(){
    $(this).show();
}).ajaxStop(function() {
    $(this).hide();
});

$("#content1").html("<img style="margin-left: auto; margin-right: auto;" src="ajax-loader.gif" alt="Loading..." title="Loading..." />");