var winCol = new Date();
function wshow(url, width, height) {
    if (!width) width = 640;
    if (!height) height = 480;
    window.open(url, (winCol++), 
                'toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=yes,resizable=yes,width=' 
                + width + 
                ',height=' + height + 
                ',left=' + ((screen.width - width) / 2) + 
                ',top=' + ((screen.height - height) / 2));
    return false;
}