La estructura de mi HTML:
<center>
<table summary="Menu Desplegable." cellspacing="0px">
<thead summary="Sejillas De Menù">
<tr>
<th><i>Mi Desplegable1</i></th>
<td><input type="button" onclick="Despliega Contabla0"></td>
<th><i>Mi Desplegable2</i></th>
<td><input type="button" onclick="Despliega Contabla1"></td>
<th><i>Mi Desplegable3</i></th>
<td><input type="button" onclick="Despliega Contabla2"></td>
</tr>
</thead>
<tbody id="Contabla0">
<tr>
<td><input type="button" onclick="Enlace()" value="Mi Enlace1"></td>
<td><input type="button" onclick="Enlace()" value="Mi Enlace2"></td>
<td><input type="button" onclick="Enlace()" value="Mi Enlace3"></td>
<td><input type="button" onclick="Enlace()" value="Mi Enlace4"></td>
</tr>
</tbody>
<tbody id="Contabla1">
<tr>
<td><input type="button" onclick="Enlace()" value="Mi Enlace1"></td>
<td><input type="button" onclick="Enlace()" value="Mi Enlace2"></td>
<td><input type="button" onclick="Enlace()" value="Mi Enlace3"></td>
<td><input type="button" onclick="Enlace()" value="Mi Enlace4"></td>
</tr>
</tbody>
<tbody id="Contabla2">
<tr>
<td><input type="button" onclick="Enlace()" value="Mi Enlace1"></td>
<td><input type="button" onclick="Enlace()" value="Mi Enlace2"></td>
<td><input type="button" onclick="Enlace()" value="Mi Enlace3"></td>
<td><input type="button" onclick="Enlace()" value="Mi Enlace4"></td>
</tr>
</tbody>
</table>
Mi CSS Es:
*{padding:0 px;margin:0 px;border:0 px}
body{background:black}
table thead{color:gray;border-color:gray;border:1px solid;background-color:silver;text-decoration:none;float:left}
table tbody a{color:gray;border-color:gray;border:1px solid;background-color:silver;width:100%;text-decoration:none;float:left}
table tbody a:hover{color:silver;border-color:silver;border:1px solid;border-left:2px solid black;border-right:2px solid black;background-color:white}
table tbody a:active{color:white;border-color:gray;border:1px solid;background-color:silver}
table tbody{background-color:dimgray;border-left:2px solid darkgray;border-right:2px solid gray;width:25%}
.input{background-color:transparent}
#hora{background-color:transparent;color:black;margin-left:34%;text-align:center;width:65px;border-bottom:2px solid silver;border-left:2px solid gray;border-top:2px solid silver}
#fecha{background-color:transparent;color:black;margin-right:34%;text-align:center;width:65px;border-bottom:2px solid silver;border-right:2px solid gray;border-top:2px solid silver}
#campo1{color:dimgray;background-color:transparent;text-align:center}
table{width:99.9%}
table thead tr th{width:20%}
table tbody tr td{text-align:center}
table thead tr td{text-align:center;width:5%}
table thead tr td input{background-color:transparent;color:silver}
table tbody tr td input{background-color:transparent;color:gray}
#head tr th{text-align:center;color:darkgray;width:90%;background-color:dimgray}
#head tr td{width:5%;background-color:dimgray}
#contabla1{float:left}
#contabla0{float:left}