function popup_big_win(url)
{
    var w = "800";
    var h = screen.height * 0.7;
    var x = (screen.width - w) * 0.5;
    var y = (screen.height - h) * 0.1;

    var winProps =
    "toolbar=yes,location=yes,status=no,menubar=yes,scrollbars=yes,resizable=yes,componentbar=no,navigationbar=no";
    var args = "width=" + w + ",height=" + h
        + "," + winProps
        + ",screenx=" + x + ",screeny=" + y
        + ",left=" + x + ",top=" + y;

    winhandle=window.open(url,'',args);
    winhandle.focus();
    return true;
}

function popup_small_win(url)
{
    var w = "500";
    var h = "400";
    var x = (screen.width - w) * 0.5;
    var y = (screen.height - h) * 0.1;

    var winProps =
    "toolbar=yes,location=yes,status=no,menubar=yes,scrollbars=yes,resizable=yes,componentbar=no,navigationbar=no";
    var args = "width=" + w + ",height=" + h
        + "," + winProps
        + ",screenx=" + x + ",screeny=" + y
        + ",left=" + x + ",top=" + y;

    winhandle=window.open(url,'',args);
    winhandle.focus();
    return true;
}

function popup_medium_win(url)
{
    var w = "700";
    var h = "500";
    var x = (screen.width - w) * 0.5;
    var y = (screen.height - h) * 0.1;

    var winProps =
    "toolbar=yes,location=yes,status=no,menubar=yes,scrollbars=yes,resizable=yes,componentbar=no,navigationbar=no";
    var args = "width=" + w + ",height=" + h
        + "," + winProps
        + ",screenx=" + x + ",screeny=" + y
        + ",left=" + x + ",top=" + y;

    winhandle=window.open(url,'',args);
    winhandle.focus();
    return true;
}