To be considered valid, an HTML document must conform to the requirements of some version of the W3C HTML spec. Among these requirements are rules about which kinds of elements may be nested inside other kinds of elements. For example:

• A list item (<li>) must be the child of a list (<ol> or <ul>) or <menu>.
• A paragraph may not contain a <section>.

TypeMetal helps you produce valid HTML files by applying these rules as you write and edit. When an action would produce invalid results, TypeMetal disallows the action, and tries to offer helpful advice.

See “HTML” for links to the relevant HTML spec documents.