带背景图片的超级链接纵向对齐问题？？

<style type="text/css">.a {
 display:block;
 width:158px;
 height:56px;
 color:#ffffff;
 text-decoration:none;
 vertical-align:middle;
 background:url(images/rigmenu.gif) no-repeat 0 0;
}
.a:hover {
 color:#ffffff;
 
 background:url(images/_rigmenu.gif) no-repeat 0 2px;</style>
---------------------
<asp:DataList ID="myDataListFloor" runat="server" RepeatColumns="1" Enabled="False" Visible="False">                   
                        <ItemTemplate>
                       <table border="0" cellpadding="0" cellspacing="0"> 
                       <tr><td>
                       <a href="#"><%#Eval("SettingName")%></a>
                                                    
                         </td></tr></table>
                        </ItemTemplate>                        
                    </asp:DataList>
=============
绑定的文字<%#Eval("SettingName")%>和背景图images/_rigmenu.gif纵向没有居中对齐，怎么改？？？