<a href="#" onclick="return alter_box_height('message', 100)">Increase Size</a>
<a href="#" onclick="return alter_box_height('message', -100)">Decrease Size</a>

<FORM>
  <TEXTAREA NAME=message style="height:100px;"></TEXTAREA>
</FORM>

<font size=-2>
  <a href="#" onclick="return alter_box_height('message', 100)">Increase Size</a>
  <a href="#" onclick="return alter_box_height('message', -100)">Decrease Size</a>
</font>

<script type="text/javascript">
function alter_box_height(objname, inc) {
  var obj = document.all[objname];
  obj.style.height = parseInt(obj.style.height) + inc + "px";
}
</script>