codice:
function mostra() {
document.getElementById("ShowNews2").style.display = "block";
document.getElementById("ShowNews3").style.display = "block";
document.getElementById("MoreNews").style.display = "none";
document.getElementById("LessNews").style.display = "block";
};
function nascondi() {
document.getElementById("ShowNews2").style.display = "none";
document.getElementById("ShowNews3").style.display = "none";
document.getElementById("MoreNews").style.display = "block";
document.getElementById("LessNews").style.display = "none";
};
// Tabella di 3 righe per 3 colonne
<tr>

 // la seconda riga la chiamo (ID) così
< tr id="ShowNews2">
 <td valign="top"><h2>.....</h2></td>
 <td valign="top">....</td>
< td valign="top">....</td>
</tr>

 // la terza riga
< tr id="ShowNews3">
 <td valign="top"><h2>.....</h2></td>
 <td valign="top">....</td>
< td valign="top">....</td>
</tr>

 // i bottoni
< td><button type="submit" id="MoreNews" name="MoreNews" onclick="mostra()"/>SHOW MORE NEWS<button>
  <button type="submit" id="LessNews" name="LessNews" onclick="nascondi()"/>SHOW LESS NEWS<button>