style.css

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

/* Tooltip text */
.tooltip .tooltiptext {
  display: none;
  visibility: hidden;
  padding: 12px;
  border-radius: 2px;
  
  position: absolute;
  z-index: 1;

  font-family: Consolas,"Andale Mono WT","Andale Mono","Lucida Console","Lucida Sans Typewriter","DejaVu Sans Mono","Bitstream Vera Sans Mono","Liberation Mono","Nimbus Mono L",Monaco,"Courier New",Courier,monospace;
  font-size: 75%;

  line-height: normal;
  background: #edf0f2;
  border: 1px solid #e1e4e5;

}

/* Show the tooltip text when you mouse over the tooltip container */
.tooltip:hover .tooltiptext {
  visibility: visible;
  display: block;
}