.cnblogs-markdown pre {
  position: relative;
}
.cnblogs-markdown pre > span {
  position: absolute;
  top: 0;
  right: 0;
  border-radius: 3px;
  padding:0 10px;
  font-size: 12px;
  background: #fff;
  color: #000;
  cursor: pointer;
  display:none;
  margin:8px 10px;
  transition: background .5s;
  -moz-transition: background .5s;
  -webkit-transition: background .5s;
  -o-transition: background .5s;
}
.cnblogs-markdown pre > span:hover {
  background: #ddd
}
.cnblogs-markdown pre:hover > span {
  display:block;
}