Code
<html>
<head>
<script>
function checkedAll (id, checked) {
var el = document.getElementById(id);
for (var i = 0; i < el.elements.length; i++) {
el.elements[i].checked = checked;
}
}
</script>
</head>
<body>
<form id="daform">
<input type="checkbox" name="foo"/>
<input type="checkbox" name="bar"/>
<a href="javascript:checkedAll('daform', true)">all</a>
<a href="javascript:checkedAll('daform', false)">none</a>
</form>
</body>
</html>