/* Tooltip container */
.tooltip {
  position: relative;
  display: inline-block;
  border-bottom: 1px dotted black;
   	font-weight: bold;  
}

.tooltip .tooltiptext {
  visibility: hidden;
  width: 280px;
  background-color: black;
  color: #fff;
  text-align: center;
  border-radius: 6px;
  padding: 5px 0;
  
  /* Position the tooltip */
  position: absolute;
  z-index: 1;
  bottom: 100%;
  left: 50%;
  margin-left: -140px; /* this is half of the WIDTH above  */
}

.tooltip:hover .tooltiptext {
  visibility: visible;
}
/*
<div class="tooltip">Hover over me
  <span class="tooltiptext">Tooltip text</span>
</div> */