CodePen Embed - qBPeved

<div class="test">Di chuột qua đây
  <span class="tooltiptext">Hello World!</span>
</div>

.test {
  position: relative;
  display: inline-block;
  border-bottom: 1px dotted black;
}

.test .tooltiptext {
  visibility: hidden;
  width: 120px;
  background-color: black;
  color: #fff;
  text-align: center;
  border-radius: 6px;
  padding: 5px 0;
  
  /* Xác định vị trí của hộp chú giải */
  position: absolute;
  z-index: 1;
  top: -5px;
  left: 105%;
}

.test:hover .tooltiptext {
  visibility: visible;
}

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