>Hi Len,
>
>Thank you very much, it is exactly I want, I'm really appreciate that your answer in very detail, as you seem that already knew I'm a very beginner in HTML. Thanks for your help.
>
>Thank You Very Much
>Aston

Mistake with my cut & paste, I realised after I went home yesterday (convert the & first, before inserting extra ones), sorry :

<script>
function validate()
{
  document.all.fld1.value = document.all.fld1.value.replace( "&", "& amp;" ) // Omit space after the &
  document.all.fld1.value = document.all.fld1.value.replace( "<", "& lt;" )  // Omit space after the &
  document.all.fld1.value = document.all.fld1.value.replace( ">", "& gt;" )  // Omit space after the &
  document.all.fld1.value="< pre>"+document.all.fld1.value+"< /pre>" // Omit space after the <
  return true
}
</script>

<form method="post" action="..." onsubmit="validate()">
<input type="text" id="fld1" name="fld1"></input>
<input type="submit" name="guestsubmit" value="Submit">Click to send
</form>