一些值如left等，還是需要寫成-22px,才有作用。
另外，設(shè)置了div里面按鈕a的寬高后，里面的span為何也會繼承這寬高??？？
.line?.button{
	display:block;
	width:180px;
	height:50px;
	line-height:50px;
	color:#2DCB70;
	font-family:Arial,?Helvetica,?sans-serif;
	text-decoration:none;
	border:2px?solid?rgba(255,255,255,0.8);
	padding-left:20px;
	box-sizing:border-box;
	position:relative;
	margin:5px?auto;
	background:url(images/allow.png)?no-repeat?130px?center;
	transition:0.3s?ease-out;
	}
.line?.button:hover{
	background-position:140px?center;
	border:2px?solid?rgba(255,255,255,1);
	}
.button?.line{
	position:absolute;
	display:block;
	background:none;
	transition:0.3s?ease-out;
	}
.button:hover?.line{background:#FFF;}
.button?.line-left{
	width:0px;
	height:2px;
	top:-2px;
	left:-110%}
.button:hover?.line-left{
	width:100%;
	left:-22px;}

.button?.line-top{
	width:2px;
	height:0px;
	top:-110%;
	right:-22px;}
.button:hover?.line-top{
	height:100%;
	top:-2px;}

.button?.line-right{
	width:0px;
	height:2px;
	bottom:-2px;
	right:-110%;}
.button:hover?.line-right{
	width:100%;
	right:-22px;}

.button?.line-bottom{
	width:2px;
	height:0px;
	bottom:-110%;
	left:-22px;}
.button:hover?.line-bottom{
	height:100%;
	bottom:-2px;}