Questi (un misto di errori e warnings) :):

line 30 column 7 - Error: discarding unexpected </form>
line 30 column 14 - Error: discarding unexpected </td>
line 33 column 1 - Warning: missing </font> before </td>
line 37 column 7 - Warning: <font> unexpected or duplicate quote mark
line 37 column 7 - Warning: <font> unexpected or duplicate quote mark
line 47 column 74 - Warning: missing </font> before </td>
line 47 column 66 - Warning: plain text isn't allowed in <tr> elements
line 66 column 7 - Warning: <font> unexpected or duplicate quote mark
line 66 column 7 - Warning: <font> unexpected or duplicate quote mark
line 76 column 74 - Warning: missing </font> before <form>
line 76 column 144 - Warning: inserting implicit <font>
line 76 column 144 - Warning: missing </font> before <center>
line 76 column 156 - Warning: inserting implicit <font>
line 85 column 7 - Warning: <font> unexpected or duplicate quote mark
line 85 column 7 - Warning: <font> unexpected or duplicate quote mark
line 106 column 7 - Warning: <font> unexpected or duplicate quote mark
line 106 column 7 - Warning: <font> unexpected or duplicate quote mark
line 116 column 74 - Warning: missing </font> before </td>
line 116 column 66 - Warning: plain text isn't allowed in <tr> elements
line 125 column 7 - Warning: <font> unexpected or duplicate quote mark
line 125 column 7 - Warning: <font> unexpected or duplicate quote mark
line 135 column 91 - Warning: missing </a> before <p>
line 135 column 74 - Warning: missing </font> before <p>
line 136 column 4 - Warning: inserting implicit <font>
line 136 column 4 - Warning: missing </a> before <p>
line 136 column 4 - Warning: missing </font> before <p>
line 137 column 4 - Warning: inserting implicit <font>
line 137 column 4 - Warning: missing </a> before <p>
line 137 column 4 - Warning: missing </font> before <p>
line 138 column 4 - Warning: inserting implicit <font>
line 138 column 4 - Warning: missing </a> before <p>
line 138 column 4 - Warning: missing </font> before <p>
line 139 column 4 - Warning: inserting implicit <font>
line 139 column 4 - Warning: missing </a> before <p>
line 139 column 4 - Warning: missing </font> before <p>
line 155 column 94 - Warning: unescaped & or unknown entity "&d_op"
line 155 column 105 - Warning: unescaped & or unknown entity "&lid"
line 161 column 94 - Warning: unescaped & or unknown entity "&d_op"
line 161 column 105 - Warning: unescaped & or unknown entity "&lid"
line 166 column 94 - Warning: unescaped & or unknown entity "&d_op"
line 166 column 105 - Warning: unescaped & or unknown entity "&lid"
line 170 column 94 - Warning: unescaped & or unknown entity "&d_op"
line 170 column 105 - Warning: unescaped & or unknown entity "&lid"
line 175 column 94 - Warning: unescaped & or unknown entity "&d_op"
line 175 column 105 - Warning: unescaped & or unknown entity "&lid"
line 180 column 94 - Warning: unescaped & or unknown entity "&d_op"
line 180 column 105 - Warning: unescaped & or unknown entity "&lid"
line 208 column 7 - Warning: <font> unexpected or duplicate quote mark
line 208 column 7 - Warning: <font> unexpected or duplicate quote mark
line 218 column 74 - Warning: missing </font> before </td>
line 218 column 66 - Warning: plain text isn't allowed in <tr> elements
line 227 column 7 - Warning: <font> unexpected or duplicate quote mark
line 227 column 7 - Warning: <font> unexpected or duplicate quote mark
line 237 column 74 - Warning: missing </font> before </td>
line 237 column 66 - Warning: plain text isn't allowed in <tr> elements
line 246 column 7 - Warning: <font> unexpected or duplicate quote mark
line 246 column 7 - Warning: <font> unexpected or duplicate quote mark
line 256 column 299 - Warning: inserting implicit <font>
line 256 column 299 - Warning: replacing unexpected iframe by </iframe>
line 256 column 178 - Warning: missing </iframe>
line 256 column 74 - Warning: missing </font> before </td>
line 256 column 66 - Warning: plain text isn't allowed in <tr> elements
line 265 column 7 - Warning: <font> unexpected or duplicate quote mark
line 265 column 7 - Warning: <font> unexpected or duplicate quote mark
line 275 column 74 - Warning: missing </font> before <form>
line 275 column 145 - Warning: inserting implicit <font>
line 275 column 145 - Warning: missing </font> before <table>
line 283 column 9 - Warning: inserting implicit <font>
line 283 column 9 - Warning: missing </font> before <center>
line 283 column 21 - Warning: inserting implicit <font>
line 292 column 14 - Error: discarding unexpected </td>
line 292 column 19 - Error: discarding unexpected </tr>
line 292 column 24 - Error: discarding unexpected </table>
line 292 column 32 - Warning: missing </font> before <p>
line 293 column 19 - Warning: inserting implicit <font>
line 298 column 1 - Error: discarding unexpected </font>

Mmmm, e come faccio a trovarli e toglierli...?

Beh... per trovarli te li ho segnalati io, c'è anche la riga.
Cmq puoi andare sul sito http://validator.w3.org/ inserire l'indirizzo del sito e guardare gli errori con anche i consigli sulla sistemazione (in inglese).

Si beh gli errori li ho corretti tutti tranne:
line 292 column 14 - Error: discarding unexpected </td>
line 292 column 19 - Error: discarding unexpected </tr>
line 292 column 24 - Error: discarding unexpected </table>

perchè non riesco a trovare il file in cui questi comandi vengono chiusi, però questo sito che mi dici mi sembra un pò severo... Nella home page di google segna 75 errori!

Non è severo... sono le linee guida che dovrebbero essere rispettate

Strano... a me la home page di google (vista con FF) dà 24 warnings ma nessun errore.

E... se conosci phpnuke mi sai dire dove posso trovare i file dove sono contenuti gli ultimi 3 errori? (le tabelle chiuse non aperte)

Ciao, scusa se ti rispondo in ritardo ma ho avuto 36 ore incasinate
Hai corretto, vero?

Risolti tutti tranne /table /td /tr non aperti ma solo chiusi... Non so in quali file siano...:?

xpx, scusa ma io quei moduli lì non li conosco...

Ah.. e qualcun'altro che li conoscesse? Io ho provato tutto... theme, index e altri files, ma niente...