Here is an example of how to do it:
a.tip {
border-bottom: 1px dashed;
text-decoration: none
}
a.tip:hover {
cursor: help;
position: relative
}
a.tip span {
display: none
}
a.tip:hover span {
border: #c0c0c0 1px dotted;
padding: 5px 20px 5px 5px;
display: block;
z-index: 100;
background: url(../images/status-info.png) #f0f0f0 no-repeat 100% 5%;
left: 0px;
margin: 10px;
width: 250px;
position: absolute;
top: 10px;
text-decoration: none
}
LinkThis is the CSS tooltip showing up when you mouse over the link