<script type="text/javascript">
<!--
function add(id, text) {
var itm = document.getElementById(id);
if(itm) {
var currentMessage = itm.innerHTML;
var newMessage = currentMessage+text;
itm.innerHTML = newMessage;
}
}
//-->
</script>
<textarea id="text">
</textarea>
<img src="button1.jpg" onclick="add('text', 'Hello ')">
<img src="button2.jpg" onclick="add('text', 'World! ')">