很简单的一段代码：
- HTML code
.index_av .intro { width:99px; margin-left:18px; float:left; }
.index_av .intro:first-child { margin-left:8px; }
<div class="index_av f_l">
<div class="title">Confident tutors (with video/audio presentation)</div>
<div class="intro">
<img src="/picture.php?path={%$vol.Photo%}&w=93&h=118" border="0">
</div>
<div class="intro">
<img src="/picture.php?path={%$vol.Photo%}&w=93&h=118" border="0">
</div>
<div class="intro">
<img src="/picture.php?path={%$vol.Photo%}&w=93&h=118" border="0">
</div>
<div class="intro">
<img src="/picture.php?path={%$vol.Photo%}&w=93&h=118" border="0">
</div>
<div class="intro">
<img src="/picture.php?path={%$vol.Photo%}&w=93&h=118" border="0">
</div>
</div>
针对第一个.intro, margin-left仍是18px,而不是8px;而且IE8和FF的效果都是一样的，实在想不出是什么原因。
------解决方案--------------------
.index_av .intro:first-child { margin-left:8px; }
.intro不是.index_av的第一个子元素不会有效果