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

    if (screen) {
        y = (screen.availHeight - height)/2;
        x = (screen.availWidth - width)/2;
    }
var small_window = window.open(URL,'newWin','width='+width+',height='+height+',screenX='+x+',screenY='+y+',top='+y+',left='+x+',scrollbars=yes');
small_window.focus();
}