This css class will allow you to add transparency compatibility to all major browsers, some of the newer CSS3 properties have pampered us into thinking they may be applied everywhere. Unfortunately opacity is one such example where CSS still requires some minor updates. Appending the filter property should handle any older versions of IE with grace.
filter: alpha(opacity=50); /* internet explorer */
-khtml-opacity: 0.5; /* khtml, old safari */
-moz-opacity: 0.5; /* mozilla, netscape */
opacity: 0.5; /* fx, safari, opera */