.up_down{position: fixed;
right: 3%;
bottom: 10%;
z-index: 888;
display:none;
}
.up_down a{background:rgba(0,0,0,0.5); border-radius:0.4rem; display:block;width:0.4rem;height:0.4rem;  text-align:center; color:#fff; margin-top:0.1rem;}

.up_down a:link{color:#333}


.up_down .up_sjx{
  height: 0;
  width: 0;
  border:0.08rem solid transparent;
  border-bottom: 0.08rem solid #fff;
  position:absolute;
  top:0.15rem;
  left:0.12rem;
}
.up_down .down_sjx{
  height: 0;
  width: 0;
  border:0.08rem solid transparent;
  border-top: 0.08rem solid #fff;
  position:absolute;
  top:0.77rem;
  left:0.12rem;
}