[HAB] ID already defined error

Dears

Below is a snippet of my xhtml1.1 code. When I validate, I get the
following error:


Line 40, column 29: ID "menulink" already defined

<td><a id="menulink" href="">Tools</a></td>

An "id" is a unique identifier. Each time this attribute is used in a
document it must have a different value. If you are using this attribute
as a hock for style sheets it may be more appropriate to use classes
(which group elements) than id (which are used to identify exactly one
element). 

  * Line 37, column 29: ID "menulink" first defined here

<td><a id="menulink" href="">Tutorial</a></td>

  * Line 43, column 29: ID "menulink" already defined

<td><a id="menulink" href="">About Us</a></td>

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---XHTML-----
   <tr>
      <td>Main Menu</td>
        </tr>
          <tr>
            <td><a id="menulink" href="">Tutorial</a></td>
          </tr>
           <tr>
             <td><a id="menulink" href="">Tools</a></td>
           </tr>
             <tr>
              <td><a id="menulink" href="">About Us</a></td>
          </tr>
          <tr>
             <td><a id="menulink"
                href="mailto:eeetc@bjaili.com">Contact Us</a></td>
          </tr>
----CSS2----
a#menulink:hover{
display: block;
 width: 100%;
 background: #fffFff;
 text-decoration: none;