[jQuery] toggle function failed in tomcat

[cong]

when i use   this address file:///D:/apache-tomcat-6.0.18/webapps/tree/tree.html
 it works.
when i use   http://localhost:8080/tree/tree.html
it failed.

why ? could you help me? THANK YOU!

HTML:

    <ul class="root" id="0">
        <img id="img1" src="img/plus.gif" /><img src="img/folder.gif"/>

    </ul>


custom3.js
 $(document).ready(function(){

 $(".root").toggle(function(){
$("#"+this.id+" > img:first").attr("src","img/minus.gif");

 },function(){
  $("#"+this.id+" > img:first").attr("src","img/plus.gif");

  });
        });