function openWindow(theURL,winName,width,height) {
    x = (640 - width)/2, y = (480 - height)/2;

    if (screen) {
        y = (screen.availHeight - height)/2;
        x = (screen.availWidth - width)/2;
    }

    window.open(theURL,winName,'toolbar=no,location=no,status=no,menubar=no,scrollbars=no,resizable=no,width='+width+',height='+height+',screenX='+x+',screenY='+y+',top='+y+',left='+x);
}