Why is the property opacity available for reading but not font-size?
<p>If I want to read the opacity value in to javacript I can just use </p>

<pre><code>element.style.opacity 
</code></pre>

<p>but if I want the fontSize I have to use the function below.</p>

<pre><code>function findFontSize( element_id )
{
    var element = document.getElementById( element_id );  
    // var theCSSprop = element.style.fontSize; // Does not work  
    // var theCSSprop = element.getPropertyValue("font-size"); // Does not work
    var theCSSprop = window.getComputedStyle( element, null ).getPropertyValue("font-size");  // This works
    alert( theCSSprop ); 
}
</code></pre>

<p>Related</p>

<p><a href="http://jsfiddle.net/tUc5v/" rel="nofollow">http://jsfiddle.net/tUc5v/</a></p>

<p>Why is this?</p>
