function comprobar(){
   var f = document.forms[0];
   var error = "";  //Contains the field names of the missing mandatory names

   // *** Validate the missing fields
   if (f.surname.value == "") {
      error += "Nombre ";
   }
   if (f.lastname.value == "") {
      error += "Apellidos ";
   }
   if (f.email_address.value == "") {
      error += "Correo Electrónico ";
   }


   // *** Error Alert
   if (error != "") {
      var errortext = "Los siguientes campos obligatorios no se han rellenado:\n";
      errortext += error;
      alert(errortext);
      return false;
   }
   alert("test");
   return true;
}


function random_intervall(a, b) {
  var z = Math.random();
  z *= (b - a + 1);
  z += a;
  return(Math.floor(z));
}

function print_reference() {
  
   var texts = new Array();

   texts[texts.length] = '"I want to recommend Diego as he has been a reliable and very well marketing knowledge skilled person." Giuseppe Gigante, Marketing Manager, Panda Security Italia';
   texts[texts.length] = '"Diego is an excellent Product Marketing Manager from our Spain office with solid English skills and has my endorsement." Carol M. Adams, VP, Marketing, Panda Security Inc.';
   texts[texts.length] = '"Diego reported to me for some months as Product Marketing Manager. He is a honest, hard worker and really committed and accountable professional. He is a very good team member as well."Jose Antonio Lopez Sanz, Director of Corporate Solutions, Panda Security';
   texts[texts.length] = '"Diego is a great proffesional really product-oriented. Besides, he is a great team driver. All the help he could provide for accomplishing any project was given in the most efficient way. I would recommend Diego as your next marketing team member." Iria Villar, Business Development, Technology Partnerships Manager, Panda Security';
   texts[texts.length] = '"Diego is one of the most committed and involved person with whom I have ever worked. He is very serious with his tasks, but at the same time, working with him can be very funny. He is a great professional." Amaia Roldan, Corporate Products Certification Manager, Panda Security';
   texts[texts.length] = '"Diego is a great professional, with both technical and marketing skills. It was great working with him." Bruno Rodriguez , Business Unit Director , Panda Security';
   texts[texts.length] = '"Diego is a very professional person, with very good technical and relational background, and team spirit . It was a real pleasure working with him." Dominique Morice, Key Account Manager, Seeburger France';
   texts[texts.length] = '"Recomiendo a Diego por su enorme inteligencia y habilidad personal, manifestada en una gran empatía y capacidad para identificar las necesidades de sus clientes, transmitiendo confianza y comprometiéndose con su palabra." Aristóteles Cañero Villegas was a consultant or contractor to Diego at SEEBURGER';

 
   var t = texts.length - 1;
   var casualidad = random_intervall(0, t);

   document.write(texts[casualidad]);
   //document.write(texts[7]);

}