Javascript createPopup

Create Popup to show loading data

function showLoading() {
        var m = window.createPopup();
        var n = m.document.body;
        var width=200;
        var height=100;
        var left = parseInt((screen.availWidth/2) - (width/2));
        var top = parseInt((screen.availHeight/2) - height);
        n.style.border="solid 2px black";
        n.innerHTML = "Loading Data ....";
        m.show( left, top, width, height, document.body);
}