#backTop{color:#D71921;cursor:pointer;display:none;height:40px;line-height:40px;padding:10px;text-align:center;width:40px;z-index:999999999;
	-moz-border-radius:50%; 
	-webkit-border-radius:50%;
	border-radius:50%;
	-webkit-box-sizing:content-box;
	box-sizing:content-box;
}
.black{background:rgba(255,203,5,0.5);}
.black:hover{background:rgba(255,203,5,1);}