WC3 icon link

Hi all,

I just wrote some HTML code and successfully validated it using the WC3 MarkUp Validation Service. In the results page there is a paragraph with the following note: 

To show your readers that you have taken the care to create an interoperable Web page, you may display this icon on any page that validates. Here is the HTML you could use to add this icon to your Web page: 

    <p>
      <a href="http://validator.w3.org/check/referer"><img border="0"
          src="http://www.w3.org/Icons/valid-html401"
          alt="Valid HTML 4.01!" height="31" width="88"></a>
    </p>
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I included the above HTML code but the URL in the href attribute is not valid. A page is displayed with the following error message:
Sorry, this type of URI scheme (undefined) is not supported by this service. Please check that you entered the URI correctly. 

URIs should be in the form: http://validator.w3.org/

If you entered a valid URI using a scheme that we should support, please let us know as outlined on our Feedback page. Make sure to include the specific URI you would like us to support, and if possible provide a reference to the relevant standards document describing the URI scheme in question. 

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Actually if I click on the WC3 icon in any of your pages the error page is displayed. This URL is incorrect. Please let me know which is the right one.

Thanks,
Roberto