l>
<li>An
          "<code title="U+0026 AMPERSAND">&amp;</code>"
          character.</li>
          <li>A
          "<code title="U+0023 NUMBER SIGN">#</code>"
          character.</li>
          <li>Either a
          "<code title="U+0078 LATIN SMALL LETTER X">x</code>"
          character
          or a
          "<code title="U+0058 LATIN CAPITAL LETTER X">X</code>"
          character.</li>
          <li>One or more digits in the range
          <code title="U+0030 DIGIT ZERO&#8211;U+0039 DIGIT NINE">