怎样用javascript删除用户选定的表格行?
<!DOCTYPE   html   PUBLIC    "-//W3C//DTD   XHTML   1.0   Transitional//EN "    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">  
  <html   xmlns= "http://www.w3.org/1999/xhtml ">  
  <head>  
  <meta   http-equiv= "Content-Type "   content= "text/html;   charset=gb2312 "   />  
  <title> Untitled   Document </title>  
  <script   language= "javascript ">  
 var   rowIndex   =   0; 
 function   AddOneLine(str1)    
 { 
 	var   row   =   userlist.insertRow(userlist.rows.length);   
 	var   col   =   row.insertCell(0); 
 	col.innerHTML   =    " <input   name= 'checkbox '   type= 'checkbox '   value= ' "+rowIndex+ " '   id= 'checkbox_ "+rowIndex+ " '   />  "; 
 	col.setAttribute( "align ", "center "); 
 	col   =   row.insertCell(1); 
 	col.innerText   =   rowIndex; 
 	col.setAttribute( "align ", "center ");     
 	row.setAttribute( "id ",    "row "+rowIndex);    
 	row.setAttribute( "name ",    "row "+rowIndex); 
 	rowIndex++; 
 }   
 //清空电话列表 
 function   clearlist(){ 
 	var   p=0; 
 	var   ls_t=document.all( "userlist "); 
 	while   (p <userlist.rows.length){ 
 	      	if   (document.getElementById( "checkbox_ "+p).checked==true){ 
 				ls_t.deleteRow(p); 
 				p=0; 
 		}else{ 
 				p++;	 
 		} 
 	} 
 } 
  </script>  
  </head>    
  <body>  
  <input   name= "add "   type= "button "         onclick= "AddOneLine( '未知 ') "   value= "add "/>  
  <input   name= "del "   type= "button "   value= "del "      onclick= "clearlist() "/>  
 			 <div   style= "overflow:auto;   width:100%;   height:220 ">  
 			       <table   width= "750 "   border= "0 "   cellspacing= "0 "   cellpadding= "0 "   id= "userlist ">  
 			       <th   width= "27 ">  </th>  
 			       <th   width= "102 ">  </th>  
 			       <th   width= "80 ">  </th>  
 			       <th   width= "67 ">  </th>  
 			       <th   width= "63 ">  </th>  
 			       <th   width= "85 ">  </th>  
 			       <th   width= "119 ">  </th>  
 			       <th>  </th>  
                                            </table> 			 
 			 </div>  
  </body>  
  </html>    
 上面这个页面想要做成当用户选中表中的checkbox后,按del按钮会删除所有选中的数据行,可是为什么会出错呢?请高手讲讲。 
------解决方案-------------------- <!DOCTYPE html PUBLIC  "-//W3C//DTD XHTML 1.0 Transitional//EN "  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">  
  <html xmlns= "http://www.w3.org/1999/xhtml ">  
  <head>  
  <meta http-equiv= "Content-Type " content