<input type="checkbox" name="chkall" onClick="CheckAll(this.form)">选中所有

<script>
function CheckAll(form)
{
for (var i=0;i<form.elements.length;i++)
{
var e = form.elements[i];
if (e.name != 'chkall')
e.checked = form.chkall.checked;
}
}
</script>