#back-top {
	position: absolute;
	bottom: 30px; 
	right: 30px; 
	display: none;
	height: 40px;
	position: fixed;
	width: 40px; 
	z-index: 100; 
	text-indent: -9000px;
	-webkit-border-radius: 2px; 
	-moz-border-radius: 2px;
	border-radius: 2px; 
	z-index: 10000;
	overflow: hidden;
	opacity: 0.4;
	filter: alpha(opacity=40); /* 针对 IE8 以及更早的版本 */
	background-color: #7CD9D9;
	background-image: url(arrow-up.png);
	background-repeat: no-repeat; 
	background-position: center center;
}

		@media screen and (max-width: 736px) {
			#back-top {
				bottom: 15px; 
				right: 15px; 
			}
		}


 
#back-top:hover { 
	background-color: rgba(239, 131, 118, 0.75);
}