function popup(winURL, winTitle, winWidth, winHeight)
{
    winLeft=(screen.width)?(screen.width-winWidth)/2:100;
    winTop=(screen.height)?(screen.height-winHeight)/2:100;
    winProperties = "width=" + winWidth + ",height=" + winHeight + ",top=" + winTop + ",left=" + winLeft;
    window.open(winURL, winTitle, winProperties);
}