JS, selecting a div's child
<p>If I have</p>

<pre><code>function OnMouseIn (elem) {
            elem.style.display= "block";
        }


&lt;div onmouseover="OnMouseIn (this.XXXXXXX)"&gt;
    &lt;div class="classname" style="display:none"&gt;&lt;/div&gt;
&lt;/div&gt;
</code></pre>

<p>What do I have to write in place of XXXXXXX to select the div's child "classname"? (note: there are a lot of the first div, and i have to select only the one where the mouse just got over.</p>
