JS新手，问几个问题

Question

补多一个小问题，让层有透明度，CSS怎么写？

Answer 1

filter:alpha(opacity=60);
<DIV ID=xxmenudiv z-index:10 
oncontextmenu='window.event.returnValue=false;xxmenudiv.style.visibility="hidden";'
style="background-color:menu; 
    position:absolute;
    top:0;
    left:0;
    width:100%;
    height:100%;
    overflow:auto;">
</div>

Answer 2

filter:alpha(opacity=60);
<DIV ID=xxmenudiv z-index:10 
oncontextmenu='window.event.returnValue=false;xxmenudiv.style.visibility="hidden";'
style="background-color:menu; 
    filter:alpha(opacity=60);
    position:absolute;
    top:0;
    left:0;
    width:100%;
    height:100%;
    overflow:auto;">
</div>