function popup(url, width, height, name)
{
    var xPos   = (screen.availWidth - width)  / 2;
    var yPos   = (screen.availHeight - height) / 2 - 20;

    if (! name)
    {
        var name   = Math.random().toString(16).substr(3, 10);
    }

    if (navigator.appVersion.indexOf("Mac") != -1 && navigator.appVersion.indexOf("MSIE") != -1)
    {
        // width  -= 16;
        // height -= 16;
    }

    mywin = window.open(url, name, 'width=' + width + ',height=' + height + ',innerWidth=' + width + ',innerHeight=' + height + 'resizable=no, scrollbars=no');

    if (mywin)
    {
        mywin.focus();
        mywin.moveTo(xPos, yPos);
    }
    else
    {
        // location.href = url;
    }
}