a.tt{
position:relative;
z-index:24;
color:#3CA3FF;
font-weight:bold;
text-decoration:none;
}
a.tt span{ display: none; }
    /*background:; ie hack, something must be changed in a for ie to execute it*/
       a.tt:hover{ z-index:25; color: #aaaaff; background:;}
       a.tt:hover span.tooltip{
       display:block;
     position:absolute;
       top:0px; left:0;
       padding: 15px 0 0 0;
       width:200px;
       color: #993300;
       text-align: center;
       filter: alpha(opacity:90);
       KHTMLOpacity: 0.90;
       MozOpacity: 0.90;
       opacity: 0.90;
       }
       a.tt:hover span.top{
       display: block;
       padding: 30px 8px 0;
       background: url(bubble.gif) no-repeat top;
       }
       a.tt:hover span.middle{ /* different middle bg for stretch */
       display: block;
       padding: 0 8px;    
       background: url(bubble_filler.gif) repeat bottom;    
       }
       a.tt:hover span.bottom{
       display: block;
       padding:3px 8px 10px;
       color: #548912;
       background: url(bubble.gif) no-repeat bottom;
       }
     

<a href="#" class="tt">
       Тут текст термина (который нуждается в подсказке)
       <span class="tooltip">
       <span class="top">
       </span>
       <span class="middle">
       Тут текст всплывающей подсказки
       </span>
       <span class="bottom">
       </span>
       </span>
       </a>