Basic HTML Document Structure - jpjohnsonjr/learning-notes GitHub Wiki
Must start with <!doctype html> (this is largely historical - used to be to render a page that does not follow HTML standards. Otherwise, the browser will put the page into the "quirks" mode and will not render it appropriately.
Contain metadata about the content. For example: <meta charset="utf-8"> specifies the character set that the browser should use to render the page. Also, <title> -- a required tag.