#backTop{width:35px;height:35px;padding:10px;border-radius:4px;text-indent:-9999px;cursor:pointer;z-index:999999999;display:none;box-sizing:content-box;-webkit-box-sizing:content-box;}
#backTop.white{background:url(../img/uparr-48-b.png) no-repeat center center rgba(255,255,255,0.8);border:1px solid #ccc;}
#backTop.black{background:url(../img/uparr-48-w.png) no-repeat center center rgba(0,0,0,0.8);border:1px solid #ccc;}
#backTop.red{background:url(../img/uparr-48-w.png) no-repeat center center #1abc9c;border:1px solid #fff;}
#backTop.green{background:url(../img/uparr-48-b.png) no-repeat center center rgba(81,217,187,0.9);border:1px solid #fff;}