I have two option have a look and let me know if this is fine with you
1. Insert a blank label just beside the button and make it invisible by default , whenever u make the button invisible just make this label which is of same dimension as that of button.
2. Place the different controls in 'td'
eg:
if i have 1 button , 1 label , 1 textbox then :
<table>
<tr>
<td>
place button over here
<td>
place label over here
</td><td>
place textbox over here
</td>
</tr>
</table>