Provo a riscriverlo rispettando la DTD XHTML 1.0 Strict:
codice:
<form method="get" action="http://www.google.it/custom">
<fieldset><legend>Cerca con Google</legend>
   <a href="http://www.google.com/">
      
   </a>
   <label for="q">Parola:</label> <input type="text" id="q" name="q" size="10" maxlength="255" />
   <input type="submit" id="sa" name="sa" value="Vai" />
   <input type="hidden" id="client" name="client" value="pub-9499220534609351" />
   <input type="hidden" id="forid" name="forid" value="1" />
   <input type="hidden" id="ie" name="ie" value="ISO-8859-1" />
   <input type="hidden" id="oe" name="oe" value="ISO-8859-1" />
   <input type="hidden" id="cof" name="cof" value="GALT:#008000;GL:1;DIV:#336699;VLC:663399;AH:center;BGC:FFFFFF;LBGC:336699;ALC:0000FF;LC:0000FF;T:000000;GFNT:0000FF;GIMP:0000FF;FORID:1;" />
   <input type="hidden" id="h1" name="hl" value="it" />
</fieldset>
</form>
Spero di non aver fatto errori. Lunedì mattina...