Beim IE hilft nur JS:
HTML:
HTML-Code: 
<a href="#" class="tooltiplink" onMouseOver="tooltip('1', true)" onMouseOut="tooltip('1', false)">
Der Link
<span id="1" class="tooltip">Dein Tooltip <b>auch mit HTML</b>!!!</span>
</a>
JS:
HTML-Code: 
function tooltip(id, show) {
  if(document.all) {
    if(show) {
      document.getElementById(id).style.display='block';
    } else {
      document.getElementById(id).style.display='none';
    }
  }
}
CSS:
HTML-Code: 
span.tooltip {
  display: none;
  border: 1px solid #000000;
  background: #FFFFFF;
  font-size: 12px;
  font-family: Verdana, sans-serif;
  color: #1F1F1F;
  text-decoration: none;
  position: relative;
  left: 20px;
  top: 10px;
  z-index: 5;
  width: 200px;
  height: 50px;
}

a.tooltiplink:hover span.tooltip {
  display: block;
}
Dieses Mal ist es getestet