function valida()
{
  /*var maile = document.getElementsByName('mail');
  if (maile[0].value=="")
    alert ("OSCAR!!!");*/
    
  var mail = document.getElementById('mail');

  if (mail.value.length>2 && contarSigno('@',mail.value)==1 && contarSigno('.',mail.value)>=1 && contarSigno(' ',mail.value)==0)
  {
    document.stock.submit();
  }
  else
  {
    alert ("Debe ingresar un correo valido");
    mail.focus();
  }
    
}

function contarSigno(signo,cadena)
{
  var count=0;
  
  for (var i=0;i<=cadena.length;i++)
    if (cadena.substr(i,1)==signo)
      count++;
  
  return (count);
}