title: jQuery's change() not working
body: <p>My page has three html select tag.</p>
  
  <p>I want these three select tags to have following functions:</p>
  
  <p>When I change selectA , than selectB automatic change according selectA.
  When selectB's option has created , when I change selectB than selectC automatic change according selectB.</p>
  
  <p>( </p>
  
  <p>For example...</p>
  
  <p>first selectA's option have singer , movie star , selectB just empty.</p>
  
  <p>when singer option checked , selectB auto create option "Lady Gaga", "Celine Dion" , "Whitney Houston", If three singers have created , when I checked "Lady Gaga" , the selectC will create "birthday" , "Facebook" , "google+" options.</p>
  
  <p>when movie star option checked , selectB auto create option "Bruce Willis" , "Matt Damon" , "Will Smith", If three movie stars have created , when I checked "Bruce Willis" , the selectC will create "birthday" , "Facebook" , "google+" options. </p>
  
  <p>)</p>
  
  <p>My problem is...when I change selectB , $("#selectB_id").change() not work </p>
  
  <p>The following is my javascript code:</p>
  
  <pre><code>$(function(){
  $("#lineselect").change( function() {
      $.ajax({
          url: '/lineflow/ajaxgetselect',
          type:'POST',
          data:{ service_id:$("#lineselect option:checked").val() , level:1 },
          success: function( res ){
              var obj = jQuery.parseJSON(res);
  
              if( $("#lineselect").val() == 0 )
              {
                  $("#second_li").html("");
                  $("#third_li").html("");
              }
              else if( $("#lineselect").val() == 1 )
              {
                  $("#second_li").html("");
                  $("#third_li").html("");
                  $("#second_li").html('&lt;select id="service_type" name="service_type"&gt;&lt;option value="0"&gt;ALL&lt;/option&gt;&lt;/select&gt;');
                  $("#third_li").html('&lt;select id="service_name" name="service_name"&gt;&lt;option value="0"&gt;ALL&lt;/option&gt;&lt;/select&gt;');
                  for( i=0; i&lt;obj.length; i++)
                  {
                      $('#service_type').append($("&lt;option&gt;&lt;/option&gt;")
                                      .attr("value",obj[i].id)
                                      .text(obj[i].name)); 
                  }
              }
              else if( $("#lineselect").val() == 2 )
              {
                  $("#second_li").html("");
                  $("#third_li").html("");
                  $("#second_li").html('&lt;input type="text" id="url_name" name="url_name"&gt;&lt;/input&gt;');
              }
              else if( $("#lineselect").val() == 3 )
              {
                  $("#second_li").html("");
                  $("#third_li").html("");
                  $("#second_li").html('&lt;select id="url_type" name="url_type"&gt;&lt;option value="0"&gt;ALL&lt;/option&gt;&lt;/select&gt;');
                  for( i=0; i&lt;obj.length; i++)
                  {
                      $('#url_type').append($("&lt;option&gt;&lt;/option&gt;")
                                      .attr("value",obj[i].id)
                                      .text(obj[i].name)); 
                  }
              }
          },
          error: function(obj, status, err){}
  
      }); 
  
  });
  
  $("#service_type").change( function() {         // this change not work!!!
      $.ajax({
          url: '/lineflow/ajaxgetselect',
          type:'POST',
          data:{ service_id:$("#service_type option:checked").val() , level:2 },
          success: function( res ){
              var obj = jQuery.parseJSON(res);            
  
              $("#third_li").html("");
              $("#third_li").html('&lt;select id="service_name" name="service_name"&gt;&lt;option value="0"&gt;ALL&lt;/option&gt;&lt;/select&gt;');
              for( i=0; i&lt;obj.length; i++)
              {
                  $('#service_type').append($("&lt;option&gt;&lt;/option&gt;")
                                  .attr("value",obj[i].id)
                                  .text(obj[i].name)); 
              }
  
          },
          error: function(obj, status, err){}
  
      }); 
  
  });
  </code></pre>
  
  <p>});</p>