Css Opacity

[anukerala]

How to set opacity or filter in Smooth Navigational Menu for transperancy in submenu background in IE?
when i set ddsmoothmenu.css as

.ddsmoothmenu ul li
{
position: relative;
display: inline;
float: left;
background: #0a449e;
opacity: 0.9;
filter :alpha(opacity=90);
zoom: 1;

}

its woeking in chrome and FF but submenus are not displaying in IE. Why? Plss give the solution, if knows

[gwmbox]

Opacity is not IE supported - none of the IE versions do (not sure about IE9 though)