Transparência em menu

Olá, estou precisando que uma ajuda

gostaria de colocar transparência nesse menu.

o codigo tá abaixo, por favor me ajudem. (quero que qdo o mouse passe pelo menu, ele fique transparente)

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<style type="text/css">.mh { background-color : #ffffff; color : #990033; display : block; font-family : Verdana, Geneva, Arial, Helvetica, sans-serif; font-size : 11px; font-weight : bold; padding : 1px 5px 2px 4px; vertical-align : center; width : expression("100%"); text-align: center;}.mn { background : #ffffff; padding : 1px; position : absolute; z-index : 100; border: 1px solid #ffffff; text-align: center;}.mn a{ border : 1px #ffffff solid; color : #2F4F4F; display : block; font-family : Verdana, Geneva, Arial, Helvetica, sans-serif; font-size : 12px; padding : 1px 5px 2px 4px; text-decoration : none; vertical-align : center; width : expression("100%"); font-weight : normal; text-align: center;}.mn a:hover { background : #ffffff; border : 1px #ffffff inset; text-decoration : none; color : #990033; text-align: center;}.sp { border-bottom : #ffffff 1px solid; border-top : #ffffff 0px solid; margin : 2px 2px; text-align: center;} #divUpControl{position:absolute; width:320; left:10; top:10; z-index:1; text-align:center} #divDownControl{position:absolute; width:320; left:10; top:270; z-index:1; text-align:center} #divContainer{position:absolute; width:320; height:240; overflow:hidden; top:30; left:10; clip:rect(0,320,240,0); visibility:hidden} #divContent{position:absolute; top:0; left:0} </style>

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aguardo respostas,

sayonara