For example, HTML is a representation of hypertext. Rendering The form of presentation to information to the human reader. Imperatives may The implementation is not obliged to follow this in any way. This is not a mandatory part of the standard but is given as guidance for designers and to help explain the uses for which the elements were intended. Mandatory These features must be implemented in the rendering.
Features are mandatory unless otherwise mentioned.
Optional Standard HTML features which may safely be ignored by parsers. It is legal to ignore these, treat the contents as though the tags were not there. Authors should be awarethat these features may be ignored by some applications. Proposed The specification of these features is not final. They should not be regarded as part ofthe standard, but indicate possible directions for future versions.