#myBtn {
  display: none;
  position: fixed;
  bottom: 20px;
  right: 20px;
  z-index: 99;
  font-size: 14px;
  border: 2px solid #999;
  outline: none;
  background-color: #c00000;
  color: white;
  cursor: pointer;
  padding: 15px;
  border-radius: 4px;
}
#myBtn:hover {
  background-color: #00c0c0;
}