Prova questo....
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Untitled</title>
</head>
<body>
<script language="JavaScript" type="text/javascript">
<!--
function fn(tagid){
len = tagid.length;
var lstTab = document.getElementsByTagName('TABLE');
for (i=0;i<lstTab.length;i++) {
var curTab = lstTab(i);
if (curTab.id.substr(0,len) == tagid) {
curTab.style.display="none";
}
}
}
//-->
</script>
<table summary="" id="a_1">
<tr>
<td>ffffffffffffffffffffffffffff</td>
</tr>
</table>
<table summary="" id="a_2">
<tr>
<td>ffffffffffffffffffffffffffff</td>
</tr>
</table>
<table summary="" id="a_3">
<tr>
<td>ffffffffffffffffffffffffffff</td>
</tr>
</table>
<input type="button" value="clicca" onclick="fn('a_')">
</body>
</html>