on的用法问题
因为元素是ajax输出，所以需要用到on,
但是用了on还是没效果，请大家帮忙看看写法哪里错了，
需要达到效果：鼠标移动到元素上弹出对话框，代码如下

 $(document).on("hover","#menutest2", function(){
 
                   alert ("有效");

  });

$('#menutest2').live('hover', function() {
  alert ("有效"); 
});

$(document).on("mouseenter","#menutest2", function(){
                  
                   alert ("in");
 
  });
$(document).on("mouseleave","#menutest2", function(){
    
    alert ("out");

});

<script>
$(document).ready(function(e) {
    $(document).on('mouseover','#menutest2', function(){     
        alert ("有效");
});
});
</script>