An SGML document type definition declares element types that represent structures or desired behavior. HTML includes element types that represent paragraphs, hypertext links, lists, tables, images, etc. The HTML DTD indicates for each element type whether the start tag and end tag are required. Some HTML element types have no content. Such empty elements never have end tags.
Element names are always case-insensitive.
This is the first paragraph. This is the paragraph. Elements are not tags. For instance, the HEAD element is always present, even though both start and end HEAD tags may be missing in the markup. All the element types declared in this specification are listed in the element index .