function validar(formulario) {

 if (formulario.nombre.value.length < 4) {
    alert("Please enter your Full name.");
    formulario.nombre.focus();
    return (false);
  }
 
 if (formulario.ciudad.value.length < 4) {
    alert("Please enter your city.");
    formulario.ciudad.focus();
    return (false);
  }

  
  

 if (formulario.telefono.value.length < 9) {
    alert("Please enter your telephone number");
    formulario.telefono.focus();
    return (false);
  }

 if ((formulario.email.value.indexOf ('@', 0) == -1)||(formulario.email.value.length < 5)) { 
    alert("Please enter a correct e-mail address! \"email\"."); 
    formulario.email.focus();
    return (false); 
  }

 if ((formulario.email.value.indexOf ('@', 0) == -1)||(formulario.email1.value.length < 5)) { 
    alert("Retype your \"email\"."); 
    formulario.email1.focus();
    return (false); 
  }

   if (formulario.numpersonas.value.length < 3) {
    alert("Number of people");
    formulario.numpersonas.focus();
    return (false);
  }
  if (formulario.noches.value.length < 3) {
    alert("Number of nights to stay");
    formulario.noches.focus();
    return (false);
  }



  return (true); 
}