Problem show tooltip with DataList

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C#

ASP.NET

I'm using asp.net,C# 2008 and linq to sql.I am want to show tooltip contains an image,feature of product when mouse over id of product

<asp:DataList ID="DataList1" runat="server" RepeatColumns="4">
    <ItemTemplate>
    <div id="rollover"><a><%#Eval("id") %><span><img alt="" src="<%#"folder/"+Eval("image") %>" align="left"/>note<br /><%#Eval("feature") %></span>
    </a>
    </div>
    </ItemTemplate>
    </asp:DataList>

my css:

#rollover a
{
    text-decoration: none;
}
#rollover a span
{
    visibility: hidden;
    display: block;
    position: absolute; /**adjust disjointed text position in % or px**/
    left: 10%;
    color: #FFFFFF;
    background-color: #666699;
    border: 2px solid silver;
    padding: 5px;
}
#rollover a:hover span, #rollover a:active span, #rollover a:focus span
{
    visibility: visible;
    position: absolute;
}

#rollover a:hover, #rollover a:focus
{
    text-decoration: none;
    color: #FF6600;
    visibility: visible;
}

Tooltip displayed when the mouse over id.When I select the product in the fourth column,position of tooltip doesn't change.It must appear in front of the id product 4.I just want to use css.Help me.