B. Element Prohibitions

This appendix is normative.

The following elements have prohibitions on which elements they can contain (see SGML Exclusions). This prohibition applies to all depths of nesting, i.e. it contains all the descendant elements.

a
must not contain other a elements.
pre
must not contain the img, object, big, small, sub, or sup elements.
button
must not contain the input, select, textarea, label, button, form, fieldset, iframe or isindex elements.
label
must not contain other label elements.
form
must not contain other form elements.