Cosi ?

codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
<head>
<title>Untitled</title>
<script language="JavaScript" type="text/javascript">
<!--
function pippo(aDiv) {
 aDiv.style.display = aDiv.style.display == "block" ? "none" : "block";
}
//-->
</script>

</head>
<body>
<div id="d1" style="display:block">
 <table summary="" border="1">
  <th colspan="2">Tabella 1</th>
  <tr>
  <td>11111111111111</td><td>11111111111111</td>
  </tr>
  <tr>
  <td>11111111111111</td><td>11111111111111</td>
  </tr>
  <tr>
  <td>11111111111111</td><td>11111111111111</td>
  </tr>		
 </table>
</div>
<input type="button" value="Clicca" onclick="pippo(document.getElementById('d1'))">

<div id="d2" style="display:block">
 <table summary="" border="1">
  <th colspan="2">Tabella 2</th>
  <tr>
  <td>11111111111111</td><td>11111111111111</td>
  </tr>
  <tr>
  <td>11111111111111</td><td>11111111111111</td>
  </tr>
  <tr>
  <td>11111111111111</td><td>11111111111111</td>
  </tr>		
 </table>
</div>
<input type="button" value="Clicca" onclick="pippo(document.getElementById('d2'))">

</body>
</html>