我是 html/css 的初学者。我创建了一个一级下拉菜单栏。我想从我拥有的 css 中制作第二级。由于我不确定第二级的代码，任何人都可以帮助我使用以下 css 吗？
.menu ul{
margin:0;
padding:0;
list-style:none;
}
.menu ul li {
margin:0;
height:41px;
float:left;
border-right:1px solid #efefef;
}
.menu ul li ul{
margin:0;
padding:0;
list-style:none;
}
.menu ul li ul li {
margin:0;
height:41px;
float:left;
background:#fff;
border-right:1px solid #efefef;
}
.menu ul li .dwn{
float:right;
top:-32px;
color:#505050;
margin-right:10px;
position:relative;
cursor:pointer;
}
.menu ul li a{
padding:9px 28px 8px 28px;
display:block;
text-decoration:none;
color:#303030;
}
.menu ul li a:hover{
background:url(images/menu_hover_bg.png) repeat-x;
}
.menu ul li .act{
background:url(images/menu_hover_bg.png) repeat-x;
}
.menu ul li a span{
width:24px;
height:24px;
display:inline-block;
}
#menu li{
position: relative;
}
#menu li:hover > ul{
display: block;
}
#menu ul{
list-style: none;
margin:0;
padding:0;
display:none;
position:absolute;
top:41px;
z-index:99999;
background: #f5f5f5;
background: -moz-linear-gradient(top, #fcfcfc 0%, #f5f5f5 100%);
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#fcfcfc), color-stop(100%,#f5f5f5));
background: -webkit-linear-gradient(top, #fcfcfc 0%,#f5f5f5 100%);
background: -o-linear-gradient(top, #fcfcfc 0%,#f5f5f5 100%);
background: -ms-linear-gradient(top, #fcfcfc 0%,#f5f5f5 100%);
background: linear-gradient(to bottom, #fcfcfc 0%,#f5f5f5 100%);
-moz-border-radius: 2px;
border-radius: 2px;
border-left:1px solid #d9d9d9;
-moz-box-shadow: 2px 2px 2px rgba(0,0,0,0.5);
-webkit-box-shadow: 2px 2px 2px rgba(0,0,0,0.5);
box-shadow: 2px 2px 2px rgba(0,0,0,0.5);
}
#menu ul li{
float: none;
margin: 0;
padding: 0;
width:auto;
display: block;
}
#menu ul .active{
background: #fff9dc;
font-weight:bold;
}
#menu ul a{
border-bottom:1px solid #f4f4f4;
height: 23px;
display: block;
padding-left:30px;
white-space: nowrap;
float: none;
text-transform: none;
font-size:14px;
text-decoration:none;
color:#303030;
}