应该是div:div_pop失去焦点时触发了onover方法,比如说alert什么你去点确定div:div_pop就失去了焦点,下面代码好像正常<div id="div_pop" border="1" onmousemove="onover()" onmouseout="onout()" style="width:283px;height:30px;"> 
  <table id="tab_UserInfo" border="1" width="283px" > 
      <tr style="height:200px;"> 
          <td colspan="2"> </td> 
      </tr> 
      <tr> 
          <td> </td> 
          <td> <input id="Button1" type="button" value="button" /> </td> 
      </tr> 
  </table> 
</div> <script  language="javascript">     function $(id){
        return document.getElementById(id);
    }
    
function onover() 

 $("show").innerHTML="onover:"+event.srcElement.id;
} function onout() 

 $("show").innerHTML="onout:"+event.srcElement.id;}</script>
<div id="show"></div>