Here is a helpful reference for you:
http://msdn.microsoft.com/en-us/library/ms532847(VS.85).aspx
To utilize -ms-filter, follow these instructions:
Keep in mind that the css filter needs to be specified either as an inline style attribute or through a class. Otherwise, the filters.item property will not be accessible.
Below is some sample code:
<style>
.macska
{
opacity:1;
-ms-filter:"progid:DXImageTransform.Microsoft.Alpha(opacity=100)";
filter:alpha(opacity=100);
}
</style>
<div id="xxx" style="background-color: #CCC; filter:progid:DXImageTransform.Microsoft.Alpha(opacity=100)" class="macska">
CONTENT
</div>
<script>
o = document.getElementById('xxx');
o.filters.item("DXImageTransform.Microsoft.Alpha").opacity = 20;
</script>
Please note that the following code will not function correctly:
<style>
.macska
{
opacity:1;
-ms-filter:"progid:DXImageTransform.Microsoft.Alpha(opacity=100)";
filter:alpha(opacity=100);
}
</style>
<div id="xxx" style="background-color: #CCC;>
CONTENT
</div>
<script>
o = document.getElementById('xxx');
o.filters.item("DXImageTransform.Microsoft.Alpha").opacity = 20;
</script>