Getting CSS containt using JS from <style> tag

[Lagon666]

How can i get css contains of an element.
When i use alert(document. getElementById( 'mydiv').style. opacity) it will return empty.

<style>
#mydiv{
background:#000000;
opacity:0.4;
}
</style>

<div id="mydiv">inner</div>

<script>
function getOpacity(){
alert(document.getElementById('mydiv').style.opacity); // it returns an empty message box
}
</script>

[Dormilich]

that depends on when you define and call the JS/CSS. though it could also be that you have to access those CSS with getComputedStyl e()