Sablon:WarningBox/styles.css

.warning-box {
  border: 1px solid #f00;
  background-color: #ffe6e6;
  padding: 10px;
  margin: 10px 0;
  border-radius: 5px;
  position: relative; /* Position relative to allow absolute positioning of the triangle */
}

.warning-box::before {
  content: '';
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 10px 10px 10px 0;
  border-color: transparent #ffcc00 transparent transparent;
  position: absolute;
  left: -10px;
  top: 50%;
  transform: translateY(-50%);
}