<label><input type="button" name="select" onclick="selectAll()" value="全選"/></label>
<label><input type="button" name="select" onclick="selectAll1()" value="取消全選"/></label>

<script type="text/javascript">
function selectAll(){
var a = document.getElementsByTagName("input");
for(var i = 0;i<a.length;i++){
if(a[i].type == "checkbox") a[i].checked = true;
}
}
function selectAll1(){
var a = document.getElementsByTagName("input");
for(var i = 0;i<a.length;i++){
if(a[i].type == "checkbox") a[i].checked = false;
}
}
</script>