jquery code
$("#readdcopy").click(function(){
$('#shiadd').html($('#readd').html());
});
html code
<tr>
<td align="right" bgcolor="#f7f7f9">Registered Addresss: </td>
<td><textarea name="readd" id="readd" class="smtext"></textarea><br /><a href="#" id="readdcopy">Copy Shipping Address</a></td>
<td align="right" bgcolor="#f7f7f9">Shipping Address: </td>
<td><textarea name="shiadd" id="shiadd" class="smtext"></textarea><br /><a href="#" id="shiaddcopy">Copy Registered Address</a></td>
</tr>