-cp-opacity

The meta-property -cp-opacity will be expanded to provide opacity values that are valid for browsers that understand CSS3 (opacity) and versions of Internet Explorer, using *filter and -ms-filter. For example, an input of:

#overlay { -cp-opacity: 0.5; }

will be output as:

#overlay {
    -ms-filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=50);
    opacity:    0.5;
    *filter:    alpha(opacity=50);
}