一个经常用到的js

<style type="text/css">
<!--
body,td,th {}{
    font-size: 12px;
}
.title_show {}{
    cursor:pointer;
    padding-left:30px;
    background:no-repeat left center;
    background-image:url(http://www.blueidea.com/articleimg/bbsimg/biggrin.gif)
}
.title_hide {}{
    cursor:pointer;
    padding-left:30px;
    background:no-repeat left center;
    background-image:url(http://www.blueidea.com/articleimg/bbsimg/redface.gif)
}

-->
</style>
<script>
function showtxt(obj,bg_img)
{
    if (document.all(obj).style.display != 'block')
    {
        document.all(obj).style.display = 'block';
        bg_img.className = 'title_show'
    }
    else 
    {
        document.all(obj).style.display = 'none'
        bg_img.className = 'title_hide'
    }

}
</script>
<table width="200" border="0" cellspacing="0" cellpadding="0">
  <tr>
    <td height="20" onMouseDown="showtxt('list1',this)" class="title_hide">发表评论</td>
  </tr>
  <tr>
    <td id="list1" style="display:none">
    <div>内容</div>
    </td>
  </tr>
</table>