求一个标签问题/50分
因为我要根据条件让页面的内容显示或者隐藏   
 我现在页面有一个tr标签的横线 
  <tr   align= "center ">  
  <td   height= "20 "   colspan= "8 ">  <hr   width= "100% "   size= "1 ">  </td>  
  </tr>    
 我想隐藏这块,就是让页面显示的时候,这个地方的空间隐藏。请问,javascript应该怎样写?
------解决方案--------------------放到div里面去,然后把div隐藏掉啊
------解决方案-------------------- <!DOCTYPE HTML PUBLIC  "-//W3C//DTD HTML 4.0 Transitional//EN ">  
  <HTML>  
  <HEAD>  
  <TITLE>  New Document  </TITLE>  
  <META NAME= "Generator " CONTENT= "EditPlus ">  
  <META NAME= "Author " CONTENT= " ">  
  <META NAME= "Keywords " CONTENT= " ">  
  <META NAME= "Description " CONTENT= " ">  
  </HEAD>  
  <SCRIPT LANGUAGE= "JavaScript ">  
  <!-- 
 var prediv= " "; 
 function showKind() 
 { 
 var e=document.form1.myselect.options[document.form1.myselect.selectedIndex].value;   
 if(prediv!= " ") 
 { 
 eval( "document.getElementById( ' "+prediv+ " ').style.display= 'none ' "); 
 eval( "document.getElementById( ' "+e+ " ').style.display= 'block ' "); 
 prediv=e;   
 } 
 else 
 { 
 eval( "document.getElementById( ' "+e+ " ').style.display= 'block ' "); 
 prediv=e;   
 }   
 } 
 //-->  
  </SCRIPT>  
  <BODY>  
  <FORM METHOD=POST ACTION= " " name= "form1 ">      
  <SELECT id= "myselect " onchange= "showKind() ">  
  <option value= " "> 请选择 </option>  
  <option value= "fruit "> 水果 </option>  
  <option value= "hobby "> 爱好 </option>  
  <option value= "book "> 喜欢的书脊 </option>      
  </SELECT>    
  <div id= "mydiv " style= "position:absolute;left:10;top:50;border:1 solid red;width:300;height:200;background-color:#cccccc ">  
  <div id= "fruit " style= "position:relative;left:0;top:10;display:none ">  
  <INPUT TYPE= "checkbox " NAME= "1 "> 苹果  <INPUT TYPE= "checkbox " NAME= "1 "> 西瓜  <INPUT TYPE= "checkbox " NAME= "1 "> 番茄 
  </div>  
  <div id= "hobby " style= "position:relative;left:0;top:10;display:none ">  
  <INPUT TYPE= "checkbox " NAME= "1 "> 打篮球 <INPUT TYPE= "checkbox " NAME= "1 "> 游泳  <INPUT TYPE= "checkbox " NAME= "1 "> 高二伏 
  </div>  
  <div id= "book " style= "position:relative;left:0;top:10;display:none ">  
  <INPUT TYPE= "checkbox " NAME= "1 "> 电脑书籍  <INPUT TYPE= "checkbox " NAME= "1 "> 杂志  <INPUT TYPE= "checkbox " NAME= "1 "> 程序 
  </div>    
  </div>  
  </FORM>  
  </BODY>  
  </HTML>    
------解决方案-------------------- <tr align= "center " style= "display:none ">  
  <td height= "20 " colspan= "8 ">  <hr width= "100% " size= "1 ">  </td>  
  </tr>
------解决方案---------