function validarformulario(form)
{
				var error = "You cannot continue if you don't write something \nin the following fields:\n\n";
				
				var campos_faltantes = "";
				
				if (form.firstname.value == "")
				{
				    campos_faltantes += "- First Name.\n";
				}
				
				if (form.lastname.value == "")
				{
				    campos_faltantes += "- Last Name.\n";
				}

				if (form.cococo.value == "")
				{
				    campos_faltantes += "- E-mail.\n";
				}
				
				if (form.address.value == "")
				{
				    campos_faltantes += "- Address.\n";
				}
				
				if (form.city.value == "")
				{
				    campos_faltantes += "- City and State.\n";
				}
				
				if (form.phone.value == "")
				{
				    campos_faltantes += "- Phone at pick-up.\n";
				}
				
				if (form.zip.value == "")
				{
				    campos_faltantes += "- Zip Code.\n";
				}
				
				if (form.passengers.value == "")
				{
				    campos_faltantes += "- Number of Passengers.\n";
				}
				
				if (    form.credit_card[0].checked == false
				     && form.credit_card[1].checked == false
				     && form.credit_card[2].checked == false
				     && form.credit_card[3].checked == false
				     && form.credit_card[4].checked == false
			       )
			          {
				        campos_faltantes += "- Type of Credit Card.\n";
			          }

				/*				
				if (form.pais.value == 0)
				{
				    campos_faltantes += "- Country.\n";
				}
				*/
				
				if ( campos_faltantes != "")
				{
				   alert(error + campos_faltantes);
				   return 0;
				}

				
                 //Funcion para validar los correos ingresados.				
				if (  form.cococo.value != "" && form.cococo.value.indexOf('@',0) == -1 ) //Verificando que haya escrito la @
				{
				   alert("\"" + form.cococo.value + "\" is not a valid e-mail address.\n Please write it again.");
				   document.formulario.cococo.focus()
				   return 0;
				}
				
				
				if (  form.cococo.value != "" && form.cococo.value.indexOf('.',0) == -1 )//Verificando que haya escrito un punto
				{
				   alert("\"" + form.cococo.value + "\" is not a valid e-mail address.\n Please write it again.");
				   document.formulario.cococo.focus()
				   return 0;
				}
				
				if ( isNaN( form.passengers.value ) ) //PARA COMPROBAR SI LA CANTIDAD DE PASAJEROS ES UN NUMERO
				{
				   alert("\"" + form.passengers.value + "\" is not a valid NUMBER for the Quantity of Passengers.\n Please write it again.");
				   document.formulario.passengers.focus()
				   return 0;
				}

				
				//AQUI COMIENZO A VALIDAR SI EL USUARIO REALMENTE ESCRIBIO UN NUMERO EN EL CAMPO CANTIDAD DE PASAJEROS
				
				/*
				valor = window.document.formulario.passengers;
				
				var es_entero;
				
				es_entero = validar_num_entero(valor);
				
				if ( es_entero == 0 )
				{
				   alert("\"" + form.passengers.value + "\" is not a valid quantity for ENTERO: "+ es_entero +" NUMBER of passengers.\n Please write it again.");
				   document.formulario.passengers.focus()
				   return 0;

				}
				
				if ( es_entero != 0 )
				{
				   alert("\"" + form.passengers.value + "\" is not a valid quantity for ENTERO: "+ es_entero +"  number of passengers.\n Please write it again!!!!!!.");
				   document.formulario.passengers.focus()
				   return 0;

				}
				*/
				
				//AQUI TERMINO DE VALIDAR SI EL USUARIO REALMENTE ESCRIBIO UN NUMERO EN EL CAMPO CANTIDAD DE PASAJEROS
				
				/*
				//AQUI VERIFICO QUE EL EMAIL SEA EL MISMO DE LA CONFIRMACIÓN
				if ( form.cococo.value != form.cococo2.value )
				{
					alert("The e-mail address written in the field \"E-mail\" \n DOESN'T MATCH with the field \"E-mail Confirmation\".\n\n Remember you should write your e-mail address\n twice in order to avoid any mistake.");
					form.cococo2.value = "";
					document.formulario.cococo2.focus();
					return 0;
				}
				*/

				
				
             document.formulario.submit();

}


function confirmarborrado(form)
{
	borrar = window.confirm('Do you really want to erase all what\n you have written in this form?');
	(borrar)?document.formulario.reset():'return false';
}

function validar_num_entero(valor)
{
     //intento convertir a entero. 
     //si era un entero no le afecta, si no lo era lo intenta convertir 
     var valor;
     valor = parseInt(valor);

      //Compruebo si es un valor numérico 
      if (isNaN(valor)) 
      { 
            //entonces (no es numero) devuelvo el valor cadena vacia 
            return 1; 
      }
      else
      {
	       
            //En caso contrario (Si era un número) devuelvo el valor 
            return 0;
      } 

}