function aviso_legal()
{
    var alto_screen=window.screen.height;
    var alto=(alto_screen-500)/2;
    var ancho_screen=window.screen.width;
    var ancho=(ancho_screen-570)/2;
    window.open("aviso_legal.html", "ventana", "toolbar=no, scrollbars=yes, menubar=no, location=no, status=no, width=570, height=500, top="+ alto +", left="+ ancho +", resizable=0");
    return false
}