">system ID</dfn>
    (the second quoted string, if any, in the doctype)
    such that the combination corresponds to one of the six
    <a href="syntax.html#deprecated-doctype" id="deprecated-doctype_xref2">deprecated doctypes</a>
    in the following
    <a id="list-of-deprecated-doctypes" href="syntax.html#list-of-deprecated-doctypes">list of deprecated doctypes</a>:</p>
    <div class="example">
      <pre>&lt;!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0//EN"&gt;
&lt;!DOCTYPE html PUBLIC "-//W3C//DTD HTML