If your icon or button has insufficient text or none at all, or it just needs some additional explanation, then you surely need a tooltip for it. Why’s that? Because, as they have proved till now, tooltips can help you improve your website usability.

It  is created own CSS tooltips: no images, no javascript.

HTML

<a href="#" class="tooltip">
  your text
  <span>Your tooltip description</span>
</a>

Why an anchor?

Just for compatibility reasons. IE6 has a problem with the :hover pseudo-class used with other elements than anchor.

If you want to use these tooltips, and anchors are not an option for you, then you can use this to trigger the tooltip for IE6:

<script type="text/javascript" src="http://code.jquery.com/jquery-latest.min.js"></script>
<script type="text/javascript">
  $(function() {
    if ($.browser.msie && $.browser.version.substr(0,1)<7)
    {
      $('.tooltip').mouseover(function(){
            $(this).children('span').show();
          }).mouseout(function(){
            $(this).children('span').hide();
          })
    }
  });
</script>

CSS

.tooltip
{
  position: relative;
  background: #eaeaea;
  cursor: help;
  display: inline-block;
  text-decoration: none;
  color: #222;
  outline: none;
}

.tooltip span
{
  visibility: hidden;
  position: absolute;
  bottom: 30px;
  left: 50%;
  z-index: 999;
  width: 230px;
  margin-left: -127px;
  padding: 10px;
  border: 2px solid #ccc;
  opacity: .9;
  background-color: #ddd;
  background-image: -webkit-linear-gradient(rgba(255,255,255,.5), rgba(255,255,255,0));
  background-image: -moz-linear-gradient(rgba(255,255,255,.5), rgba(255,255,255,0));
  background-image: -ms-linear-gradient(rgba(255,255,255,.5), rgba(255,255,255,0));
  background-image: -o-linear-gradient(rgba(255,255,255,.5), rgba(255,255,255,0));
  background-image: linear-gradient(rgba(255,255,255,.5), rgba(255,255,255,0));
  -moz-border-radius: 4px;
  border-radius: 4px;
  -moz-box-shadow: 0 1px 2px rgba(0,0,0,.4), 0 1px 0 rgba(255,255,255,.5) inset;
  -webkit-box-shadow: 0 1px 2px rgba(0,0,0,.4), 0 1px 0 rgba(255,255,255,.5) inset;
  box-shadow: 0 1px 2px rgba(0,0,0,.4), 0 1px 0 rgba(255,255,255,.5) inset;
  text-shadow: 0 1px 0 rgba(255,255,255,.4);
}

.tooltip:hover
{
  border: 0; /* IE6 fix */
}

.tooltip:hover span
{
  visibility: visible;
}

.tooltip span:before,
.tooltip span:after
{
  content: "";
  position: absolute;
  z-index: 1000;
  bottom: -7px;
  left: 50%;
  margin-left: -8px;
  border-top: 8px solid #ddd;
  border-left: 8px solid transparent;
  border-right: 8px solid transparent;
  border-bottom: 0;
}

.tooltip span:before
{
  border-top-color: #ccc;
  bottom: -8px;
}

The article source:http://www.red-team-design.com/css3-tooltips