Demo:

Spoiler:

Hướng dẫn:
Chèn đoạn sau vào Overall_footer:

Code:

<script type='text/javascript' src='http://www.c3zone.net/html-h33.htm'></script>

Chèn đoạn sau vào cuối CSS:

Code:

#dhtmlpointer, #dhtmltooltip
{
  z-index: 999;
  left: -300px; top:0px;
  visibility: hidden;
  position: absolute;
}
#dhtmltooltip
{
  border: #666 2.4px solid;
  -moz-opacity: 0.8; /* lam mo tooltip FF */
  opacity: 0.8; /* lam mo tooltip Opera */
  filter: alpha(opacity=80); /* lam mo tooltip IE */
  -moz-border-radius: 6px;
  -webkit-border-radius: 6px;
  padding: 10px;
  font-size: 10pt;
  font-family: Arial;
  background-color: white;
  width: auto;
  max-width: 340px; /* chieu rong toi da cho FF */
  width:expression( document.body.clientWidth > 340? "340px": "auto" ); /* chieu rong toi da cho IE */
  text-align:left;
}