dpts,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<meta http-equiv="Content-Language" content="ru">
<style type="text/css">
tbody tr:first-child td:last-child{
visibility: hidden;
}
</style>
</head>
<body>
<form id="tasks" action="taskssave.asp">
<table style="width:70%;border-collapse:collapse;">
<thead>
<tr>
<th>Тип задачи</th>
<th>Норма времени</th>
<th>Объект привязки</th>
</tr>
</thead>
<tbody>
<tr>
<td><center><input type="text" name="task_name" required="required"></center></td>
<td>
<center>
<select name="task_len">
<option value="5">5 мин.</option>
<option value="10">10 мин.</option>
<option value="15">15 мин.</option>
<option value="20">20 мин.</option>
<option value="25">25 мин.</option>
<option value="30">30 мин.</option>
<option value="35">35 мин.</option>
<option value="40">40 мин.</option>
<option value="45">45 мин.</option>
<option value="50">50 мин.</option>
<option value="55">55 мин.</option>
<option value="60">60 мин.</option>
<option value="90">90 мин.</option>
<option value="120">120 мин.</option>
<option value="180">180 мин.</option>
</select>
</center>
</td>
<td>
<center>
<select name="task_obj">
<option value="1">Звонки</option>
<option value="2">Контакты</option>
<option value="3">Контрагенты</option>
</select>
</center>
</td>
<td style="width: 60px;"><img border="0" alt="del" src="http://ajaxs.ru/demo/jq/add_input/delete.png" class="delete"></td>
</tr>
<tr>
<td colspan="4"><br>
<center><input type="button" value="Добавить поле" id="add" onclick="return add_new();">
<input type="submit" name="Сохранить"></center>
</td>
</tr>
</tbody>
</table>
</form>
<script>
window.addEventListener("DOMContentLoaded", function() {
var a = document.querySelector("#tasks"),
b = a.querySelector("tbody"),
d = b.querySelector("tr").cloneNode(!0);
a.querySelector("#add").addEventListener("click", function() {
var c = d.cloneNode(!0);
c.addEventListener("click", function() {
var a = event.target.classList;
a && a.contains("delete") && b.removeChild(c)
});
b.insertBefore(c, b.lastElementChild)
})
});
</script>
</body>
</html>