function ventana(pagina,ancho,alto) {
    var PosX;
    var PosY;
    PosX = (screen.availWidth - ancho)/2;
    PosY = (screen.availHeight - alto)/2;
 
    if (!window.vent2||vent2.closed) {
        vent2 = window.open(pagina,'hvuss','toolbar=no,menubar=no,scrollbars=yes,resizable=no,width='+ancho+',height='+alto+',left=' + PosX + ',top=' + PosY+''); }
    else { 
        vent2.close(); 
        vent2 = window.open(pagina,'hvuss','toolbar=no,menubar=no,scrollbars=yes,resizable=no,width='+ancho+',height='+alto+',left=' + PosX + ',top=' + PosY+'');} } 
        function cerrar() {
        if (window.top.hvuss.vent2&&!window.top.hvuss.vent2.closed) {
        close(window.top.hvuss.vent2.name);
        window.top.hvuss.vent2.close();
    } 
}