Tooltip animation effect

a.tooltip span
{
  position: absolute;
  top: 30px;
  left: 50%;
  margin-left: -76px;
  z-index: 999;
  width: 250px;
  height: auto;
  color: #fff;
  font-size: 12px;
  line-height: 20px;
  border-radius: 6px;
  padding: 2px;
  text-align: center;
  background: #000;
  border: 1px solid #808080;
  visibility: hidden;
  opacity: 0;
  -webkit-transition: all 2s ease-out 0s;
  -moz-transition: all 2s ease-out 0s;
  -ms-transition: all 2s ease-out 0s;
  -o-transition: all 2s ease-out 0s;
  transition: all 2s ease-out 0s;
}
a:hover.tooltip span
{
  visibility: visible;
  -webkit-opacity: 0.90;
  -moz-opacity: 0.90;
  opacity: 0.90;
}