这个效果蛮有用的

<style type="text/css">
.prompt_info{visibility:hidden;  position:relative;top:0;left:0; border:0px solid #333333;
}
.almain  a:link {
text-decoration:none;}
.almain{width:120px; border:0px #333333 solid; height:22px;}
.almain:hover .prompt_info{

 visibility:visible;}
 
</style>
  <div class="almain"> 
   <a href='delay_time_out.jsp?id=<%=Aes_deal_id%>'>延长发货时间</a>
   <div class="prompt_info" style="background-image:url(../image/prompt_info.png);
    background-repeat:no-repeat; background-position:0px -230px; height:60px; width:235px; padding-

left:-20px;">
     <div style=" font-size:12px; color:#666666;padding-top:24px; line-height:16px;">
       延长发货时间[<a href="#">一星期</a>]&nbsp;[<a href="#">三天</a>]   
     </div>
   </div>
      </div>