js动态增加单元格，并删除对应的单元格

<table id="table1" name="table1">
    <tr>
    <td><input type="text" name="weProvide" id="weProvide1" size="10"/></td>
    <td><input type="text" name="weProvide" id="weProvide2" size="10"/></td>
    <td><input type="text" name="weProvide" id="weProvide3" size="10"/></td>
    <td><input type="text" name="weProvide" id="weProvide4" size="10"/></td>
    <td></td>
   </tr>
  <tr>
    <td><input type="text" name="weProvide" id="weProvide5" size="10"/></td>
    <td><input type="text" name="weProvide" id="weProvide6" size="10"/></td>
    <td><input type="text" name="weProvide" id="weProvide7" size="10"/></td>
    <td><input type="text" name="weProvide" id="weProvide8" size="10"/></td>
    <td></td>
   </tr>
  <tr>
    <td><input type="text" name="weProvide" id="weProvide9" size="10"/></td>
    <td><input type="text" name="weProvide" id="weProvide10" size="10"/></td>
    <td><input type="text" name="weProvide" id="weProvide11" size="10"/></td>
    <td><input type="text" name="weProvide" id="weProvide12" size="10"/></td>
    <td><div class="red_color" onclick="insertRow1()">增加行</div></td>
   </tr>
   </table>
   <script type="text/javascript">
   		function insertRow1() {
   		var tablelength = document.getElementById("table1");
   		if(tablelength.rows.length>5) {
   			alert("不能在增加了！");
   			return false;
   		}
   		newline = document.all.table1.insertRow();
   		var newcell1 =(newline.insertCell().innerHTML='<input type="text" name="weProvide" size="10"/>');
   		var newcell2 =(newline.insertCell().innerHTML='<input type="text" name="weProvide" size="10"/>');
   		var newcell3 =(newline.insertCell().innerHTML='<input type="text" name="weProvide" size="10"/>');
   		var newcell4 =(newline.insertCell().innerHTML='<input type="text" name="weProvide" size="10"/>');
   		var newcell5 =(newline.insertCell().innerHTML='<div class="red_color" onclick="del1()">删除行</div>');
   		}
   		
   		function del1() {
   			document.all.table1.deleteRow(window.event.srcElement.parentElement.parentElement.rowIndex);
   		}
   </script>