<div class="container">
  <div class="absolute-box">這個元素相對於 .container 進行定位</div>
</div>

.container {
  position: relative;
  width: 300px;
  height: 200px;
  background-color: #e0e0e0;
}

.absolute-box {
  position: absolute;
  top: 20px;
  left: 30px;
  background-color: #FF5722;
  padding: 20px;
  color: white;
}