No el codigo en si es:
<script type="text/javascript">
function showContent() {
element = document.getElementById("content");
check = document.getElementById("check");
if (check.checked) {
element.style.display='block';
}
else {
element.style.display='none';
}
}
window.onload = showContent();
</script>
<s:checkbox id="check" name="beans.flagLago" />
<div id="div1" style="display:none">
<table border=1 id="t1">
<tr>
<td>i am here!</td>
</tr>
</table>
</div>