var myWindow;
function popUpWindow(url, width, height)
{
    var left = parseInt((screen.availWidth/2) - (width/2));
    var top = parseInt((screen.availHeight/2) - (height/2));
    var windowFeatures = "width=" + width + ",height=" + height + ",status,scrollbars,resizable,left=" +
                         left + ",top=" + top + ",screenX=" + left + ",screenY=" + top;

    if(myWindow && !myWindow.closed)
        myWindow.focus();
        
    myWindow = window.open(url, "subWind", windowFeatures);
}