<div class="cp_card">
コンテンツ
  <div class="cp_ribbon06">
    <div class="cp_ribbon">Ribbon</div>
  </div>
</div>

.cp_card {
  position: relative;/*リボンをかけたいコンテンツボックスにセット*/
  width: 300px;
  height: 300px;
  background: #ffffff;
  margin: auto;
  padding: 5px;
  box-shadow: 0 0 5px rgba(0, 0, 0, 0.3);
}
/*リボンの位置*/
.cp_ribbon06 {
  position: absolute;
  top: -6.1px;
  right: 10px;
}
/*リボンの三角形部分*/
.cp_ribbon06:after {
  position: absolute;
  content: '';
  border-top: 10px solid #4DD0E1;
  border-right: 53px solid transparent;
  border-left: 53px solid transparent;
}
/*リボン全体の背景*/
.cp_ribbon06 .cp_ribbon {
  position: relative;
  display: block;
  width: 90px;
  font-size: 1em;
  line-height: 1;
  padding: 12px 8px 10px;
  text-align: center;
  color: #ffffff;
  border-top-right-radius: 8px;
  background: #4DD0E1;
}
/*リボンの影の部分*/
.cp_ribbon06 .cp_ribbon:before,
.cp_ribbon06 .cp_ribbon:after {
  position: absolute;
  top: 0;
  content: '';
}
.cp_ribbon06 .cp_ribbon:before {
  left: -6px;
  width: 6px;
  height: 6px;
  background: #4DD0E1;
}
.cp_ribbon06 .cp_ribbon:after {
  left: -8px;
  width: 8px;
  height: 6px;
  border-radius: 8px 8px 0 0;
  background: #00ACC1;
}