Non-W3c compliant HTML

Hi all,

Perhaps a bit nitty-gritty, but I saw that the my MailChimp plugin implementation isn’t generating W3c compliant HTML (as XHTML 1.0 Strict).

There are 3 errors being flagged, all of them being:
“document type does not allow element “input” here; missing one of “p”, “h1”, “h2”, “h3”, “h4”, “h5”, “h6”, “div”, “pre”, “address”, “fieldset”, “ins”, “del” start-tag”
They are on different lines:

<input type="hidden" id="mc_submit_type" name="mc_submit_type" value="html" />
<input type="hidden" name="mcsf_action" value="mc_submit_signup_form" />
<input type="hidden" id="_mc_submit_signup_form_nonce" name="_mc_submit_signup_form_nonce" value="c889eeb4ea" />

Is this a problem in my implementation or is this the MailChimp plugin generating non-compliant HTML?

Kind regards,
Vincent