Web Design in a Nutshell, 3rd Edition

Every head element must include a title element that provides a description of the document. The head element may also include any of the following elements in any order: script, style, meta, link, object, isindex, and base. The head element merely acts as a container of these elements and does not have any content of its own.

It is recommended that HTML documents (and XHTML documents without an XML declaration) also include a meta element that specifies the content type and character encoding for the document, although this element is not required. The meta element is discussed in the upcoming “Providing Meta Data section.