ciao a tutti questo è il codice

codice:
 <hr size="1" noshade="" align="left" width="717" />
  <div class="certificati">    
 <a href="http://validator.w3.org/check?uri=referer">
</a>
   </div> 
<div id="footer">Copyright  2011<span class="foot_right"> Versione Grafica </span></div>
l'errore sta nel TAG <hr ed è il seguente



Error Line 1, Column 2: no document type declaration; will parse without validation <hr size="1" noshade="" align="left" width="717" /> ✉ The document type could not be determined, because the document had no correct DOCTYPE declaration. The document does not look like HTML, therefore automatic fallback could not be performed, and the document was only checked against basic markup syntax. Learn how to add a doctype to your document from our FAQ, or use the validator's Document Type option to validate your document against a specific Document Type.