function right(e)
{
    if (navigator.appName == 'Netscape' && (e.which == 3 || e.which == 2))
        return false;
    else if (navigator.appName == 'Microsoft Internet Explorer' && (event.button == 2 || event.button == 3))
    {
        alert("[ Warning !!!, you can't use right click ]");
        return false;
    }
    return true;
}

document.onmousedown = right;
document.onmouseup = right;