Opacity with CSS

Below is an example of HTML that displays a list and when you hover over the element a fade is placed over the div:

The style sheet entry looks like this (notice the other style name that is not used above archive-results-list):

ul.search-results-gallery li div:hover,
ul.archive-results-list li div:hover{
filter:alpha(opacity=85);
-moz-opacity:0.85;
opacity:0.85;
}