Behavior of Hidden Elements

I have noticed that while in Microsoft Internet Explorer when you have a
hidden element (such as a <div> containing text) the element is not only
hidden but also you cannot mouseover it or click the links. However, in
Mozilla, the div built using the following code...

<div style="position:absolute;visibility:hidden;"
onMouseover="this.style.visibility='visible';">
    <a href="http://www.fastwebnow.com">Fast Web Now</a>
</div>

...will show up when you place your mouse over it. Furthermore, even if you
take out the javascript onmouseover that makes the <div> visible, you can
still click the link (although you cannot see it). I couldn't find anywhere
in the specs that says how a hidden element should behave. Should the
browser keep the element totally hidden and unusable and not allow
interaction with the hidden elements or should the browser allow interaction
with a hidden element.  Does anyone know which behavior is correct or if the
w3c doesn't specify. I apologize if this is stated clearly somewhere and I
just haven't seen it.

- Sal Candido
salcandido@fastwebnow.com
http://www.fastwebnow.com