1.4 Standards Support Requirements
To conform to [DOM Level 2 - HTML] a user agent must implement all required portions of the specification. Any optional portions that have been implemented must also be implemented as described by the specification. Normative language is usually used to define both required and optional portions. (For more information, see [RFC2119].)
The following table lists the sections of [DOM Level 2 - HTML] and whether they are considered normative or informative.