我的sub-menu的背景图片为什么会是透明的？

*{
	margin:0;
	padding:0;
}

@font-face{
	font-family: "iconfont";
	src:url("../img/font/iconfont.eot");
	src:url("../img/font/iconfont.eot") format("embedded-opentype"),
	    url("../img/font/iconfont.woff") format("woff"),
	    url("../img/font/iconfont.ttf") format("truetype"),
		url("../img/font/iconfont.svg#iconfog") format("svg");
}
ul{
	list-style: none;
}

body{
	font-family: "微软雅黑";
	color:#14191e;
}
a:link,a:visited{
	text-decoration: none;
	color: #333;
}
.main{
	width:1200px;
	height: :460px;
	margin:30px auto;
	overflow: hidden;
	position: relative;
}
.banner{
	width:1200px;
	height:460px;
	overflow: hidden;
	position: relative;
}
.banner-slide{
	width:1200px;
	height:460px;
	background-repeat: no-repeat;
	position: absolute;
	display: none;
}
.slide-active{
	display: block;
}
.slide1{
	background-image:url("../img/bg1.jpg");
}
.slide2{
	background-image:url("../img/bg2.jpg");
}
.slide3{
	background-image:url("../img/bg3.jpg");
}
.button{
	position: absolute;
	width:40px;
	height: 80px;
	left:244px;
	top:50%;
	margin-top:-40px;
	background:url(../img/arrow.png) no-repeat center center;
}
.button:hover{
	background-color: #333;
	opacity: 0.8;
	filter:alpha(opacity=0.8);
}
.pre{
	transform:rotate(180deg);
}
.next{
	left:auto;
	right: 0;
}

.dots{
	position: absolute;
	right:20px;
	bottom:24px;
	text-align: right;
}
.dots span{
	/*水平排列*/
	display: inline-block;
	width:12px;
	height: 12px;
	border-radius: 50%;
	background: rgba(7,17,27,0.4); 
	margin-left: 8px;

	line-height: 12px;
	/*白色描边  内置*/
	box-shadow: 0 0 0 2px rgba(255,255,255,0.8) inset;
/*变小手*/
	cursor: pointer;
}
.dots span.active{
	box-shadow:  0 0 0 2px rgba(7,17,27,0.4) inset;
	background: #fff;
}
/*导航菜单*/
.menu-box{
	width:244px;
	height: 460px;
	position:absolute;
	left:0;
	top:0;
	background:rgba(7,17,27,0.5);
	opacity: 0.5;
	z-index: 1;
}

.menu-content{
	width:244px;
	height: 454px;
	position: absolute;
	left:0;
	top:0;
	padding-top: 6px;

	z-index: 2;
}

.menu-item{
	height: 64px;
	line-height: 66px;
	font-size: 12px;
	padding: 0 24px;
	position: relative;
}
.menu-item a:link,.menu-item a:visited{
	color:#fff;
}
.menu-item a{
	display: block;
	border-bottom: 1px solid rgba(255,255,255,0.5);
	padding: 0 8px;
	height: 63px;
}
.menu-item i{
	position: absolute;
	right: 32px;
	font-size: 24px;
	top: 2px;
	font-family: "iconfont";
	font-style: normal;
	font-weight: normal;
	color: rgba(255,255,255,0.5);
}
.sub-menu{
	width:730px;
	height: 460px;
	border:1px solid #d9dde1;
	background: #fff;
	position: absolute;
	left: 244px;
	top:0;
	z-index: 999;
	box-shadow: 0 4px 8px 0 rgba(0,0,0,0.1);

}

.inner-box{
	width:100%;
	height: 100%;
	background: url(../img/fe.png) no-repeat;
	display: none;
}

.sub-inner-box{
	width:652px;
	margin-left:40px;
	overflow: hidden;

}

.title{
	color:#f01414;
	font-size: 22px;
	line-height: 22px;
	margin:28px 0 30px 0;
	font-weight: bold;
}

.bold{
	font-weight: bold;
}
.mr10{
	margin-right: 10px;
}
.ml10{
	margin-left: 10px;
}
.sub-row{
	margin-bottom: 25px;
}
.hide{
	display: none;
}