Shadow: 80%

[The Anime King]

Heyo
I have a code that makes a shadow behind a picture.
The shadow is 100%, so everything within it, is blacked out.
How can i make the effect a bit transparent, so a little bit of the background is still shown?

Here's the code:

<style type="text/css">
.shadowcss{
position: relative;
top: -1px;
left: -1px;
filter:progid:DXImageTransform.Microsoft.dropshadow(OffX=1, OffY=1, Color='dark grey', Positive='true');
}
</style>

<script>
function updownshadow(){
if (event.srcElement.effect=="popshadow"){
shadowobj=event.srcElement
if (event.type=="mousedown"){
shadowobj.filters[0].color=shadowobj.mousedowncolor
shadowobj.style.left=shadowobj.style.top=0
}
else if (event.type=="mouseout" && event.fromElement.effect=="popshadow" || event.type=="mouseup"){
shadowobj.filters[0].color=shadowobj.mouseupcolor
shadowobj.style.left=shadowobj.style.top=shadowobj.filters[0].OffX*(-1)
}
}
}
</script>

<img src="image.jpg" class=shadowcss effect=popshadow mousedowncolor=white mouseupcolor=gray>


thnx, greetzzz tAK