/*将所有元素的默认间距清除，方便自己设置，并且可以消除ul和li的圆点*/
* {
	margin:0px;
	padding:0px;
}
body {
	font:300 14px "HelveticaNeue-Light","Helvetica Neue Light","Helvetica Neue",Helvetica,Arial,"Lucida Grande",sans-serif;
	background-color:#999999;
}
ul {
	background:#fff;
	box-shadow:0 0 10px rgba(0,0,0,0.2);
	/*x坐标，y坐标，模糊程度，颜色*/
white-space:nowrap;
	/*避免文字换行*/
}
ul li {
	position:relative;
}
ul li a {
	text-decoration:none;
	color:#777;
	padding:10px 20px;
	display:block;
	background:url(detail.png) bottom right no-repeat;
}
ul li a:only-child {
	background:none;
}
ul li:hover {
	background:#777;
}
ul li:hover > a {
	color:#fff;
}
ul li:hover > ul {
	display:block;
	/* 鼠标进入母选单後，显示子选单 */
}
nav > ul > li {
	display:inline-block;
	/* 使一级选单排成一列 */
}
ul ul {
	position:absolute;
	top:100%;
	list-style:none;
	background:#fff;
	box-shadow:0 3px 3px rgba(0,0,0,0.2);
	display:none;
}
ul ul ul {
	position:absolute;
	left:100%;
	top:0;
}