get mouse coordinates relative to a div position doesn't work in firefox
<p>Why doesn't the example code below work in my browser, firefox v. 19.0.2?</p>

<pre><code>&lt;html&gt;
&lt;head&gt;
&lt;style&gt;
#example {
position: absolute;
top: 20px;
left: 50px;
width: 300px;
height: 300px;
background-color: #C00;
}
&lt;/style&gt;
&lt;script type="text/javascript" src="http://code.jquery.com/jquery-1.9.1.js"&gt;&lt;/script&gt;
&lt;script&gt;
$("#example").mousemove(function(e) {
var xPos = e.pageX - $(this).position().left;
var yPos = e.pageY - $(this).position().top;
$("#pos").text("x: " + xPos + " / y: " + yPos);
});
&lt;/script&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;div id="example"&gt;&lt;/div&gt;
&lt;div id="pos"&gt;&lt;/div&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>

<p>I can't see the coordinates that are supposed to be in the <code>&lt;div&gt;</code> tag with ID pos.
ThanX in advance for your help.</p>
