<table border="1">
    <tr>
        <td colspan="2" align="right">
            <input name="addButton" value="添加" type="button" onclick="addRow(this)">
        </td>
    </tr>
    <tr>
        <td>label</td>
        <td><input name="aaa"><input name="deleteRow" type="button" value="delete" onclick="deleteRow(this)"></td>
    </tr>
</table>
<script language=javascript>
        function addRow(obj)
        {
                var objTbody=obj.parentNode.parentNode.parentNode
                var objTr=obj.parentNode.parentNode.nextSibling
                objTbody.appendChild(objTr.cloneNode(true))
        }
        function deleteRow(obj)
        {
            var objTr=obj.parentNode.parentNode
            var objTbody=objTr.parentNode
            if(objTbody.childNodes.length>2)
            {
                objTr.removeNode(true)
            }
        }
</script>