CSS でリボン風デザインをつくる

.example {
  position: relative;
  margin: 0 auto;
  width: 200px;
  height: 50px;
  background-color: #96c;
}

.example:before,
.example:after {
  position: absolute;
  top: 0;
  display: inline-block;
  width: 0;
  height: 0;
  border: 25px solid #96c;
  content: '';
}

.example:before {
  left: -15px;
  border-right-width: 0;
  border-left-width: 15px;
  border-left-color: transparent;
}

.example:after {
  right: -15px;
  border-right-width: 15px;
  border-right-color: transparent;
  border-left-width: 0;
}