function isValidMail(field, message)
{ 
  var goodEmail = true;
  var mail = field.value;
  
  if(mail.length>1)
  {
    pos=mail.indexOf("@");
    if(pos == -1)
    {
      goodEmail = false;
    }
    else
    {
      var domain=mail.substring(pos+1);
      if(pos<1)
        goodEmail = false;
      if(domain.indexOf(".") == -1)
        goodEmail = false;
    }
  }
  else
  {
    goodEmail = false;
  }
  
  if (goodEmail)
  { 
     return true;
  }
  else
  { 
    alert(message);
    field.focus() ;
    field.select() ;
    return false ;
  } 
} // isValidMail