各位大侠，帮忙看看，一个奇怪的问题

 <script language="javascript" type="text/javascript">
     var infodiv;
     var bigtype;
     var smalltype;
     function select()
     {
        bigtype=$("<%=ddlsearchbigtype.ClientID %>");
        smalltype=$("<%=ddlsearchsmalltype.ClientID %>")
        if(bigtype.selectedIndex!=0)
        {
             infodiv=$("info");
             var url="/ajax/select.aspx";
             var param="id="+bigtype.options[bigtype.selectedIndex].value;         
             var myAjax=new Ajax.Request(
              url,
                {
                   method: 'get',                    
                   parameters:param,
                   onCreate:onCreate,
                   onSuccess:onSuccess,
                   onFailure:onFailure,
                   onComplete:showResponse,
                   asynchronous:true
                }
                );
        }
        else
        {
          for(var i=1 ;i<smalltype.options.length;i++)
          {
             
              smalltype.options.remove(i);
          }
        }
     }
     
     function onCreate(request)
     {
      
        infodiv.show();
     }
     
     function onFailure(request)
     {  
       alert(request.responesText);
     }
     
     function onSuccess(request)
     { 
       
        infodiv.hide();
     }
     
     function showResponse(request)
     {      
        var txt=request.responseText; //获取select.aspx的页面的值 
        var array=txt.split("@"); 
          
         smalltype=$("<%=ddlsearchsmalltype.ClientID %>");
          
        var h=document.getElementById('hidden');            alert(h); 
         
        h.value="";
        smalltype.options.length=0;
        smalltype.options.add(new Option('子类类别','0'));
        for(var i=1;i<array.lenght;i++)
        {
          var id=array[i].split("#")[0];
          var name=array[i].split("#")[1];
          var op=new Option(name,id);
          alert(op);
          smalltype.options[smalltype.options.length] = op;
          alert(smalltype.options[smalltype.options.length]);
          h.value+="#"+id;
        }
     } 
     function select_1()
     {
        var h=document.getElementById('hidden');
        alert(h);
        var array=h.value.split('#')
        var h_1=document.getElementById('hidden_1')
        h_1.value='';
        h_1.value=array[smalltype.selectedIndex];
     } 
     
     
     
     
     function bigtype1(source,args)
     {
        var bigtype= $("<%=ddlsearchbigtype.ClientID %>");
         document.getElementById("<%=hid2.ClientID%>").value=bigtype.value;
     args.IsValid = bigtype.selectedIndex == 0 ? false : true;
     }
     function smalltype2(source,args)
 {
        var small = $("<%=ddlsearchsmalltype.ClientID %>");
        args.IsValid = small.selectedIndex == 0 ? false : true;
     }
     
     
     
         
    </script>
我引用了“prototype.js”，红色语句不知道什么问题？我在2005vs工程下面调试时弹出"object HTMLInputEelment"，但在2008vs工程引用进来 “prototype.js”，红色地方“NULL”为空.