.box {
    width: 300px;
    height: 300px;
    background-color: #a0a0a0;
    position: relative;
}
.ribbon {
  -webkit-transform: rotate(-45deg);
  -moz-transform: rotate(-45deg);
  -ms-transform: rotate(-45deg);
  -o-transform: rotate(-45deg);
  transform: rotate(-45deg);
  border: 25px solid transparent;
  border-top: 25px solid #757575;
  position: absolute;
  bottom: 19px;
  right: -44px;
  padding: 0 10px;
  width: 177px;
  color: white;
  font-family: sans-serif;
  size: 11px;
}
.ribbon .txt {
    position: absolute;
    top: -25px;
    left: 10px;
}