a.tooltip{
  position: relative;
  color: blue;
  text-decoration: none;
}

a.tooltip:hover{
  background-color: #FFFF99;
  color: navy;
  z-index: 1;
}

a.tooltip span{
  display: none;
}

a.tooltip:hover span{
  z-index: 2;
  display: block;
  position: absolute;
  top: 2em;
  left: 2em;
  width: 15em;
  border: 1px solid #000;
  background-color: #FFFF99;
  color: black; 
  text-align: center;
  font-size: medium;
  font-weight: normal;
}