html cannot be written in a plain text editor.

Informally, HTML elements are sometimes referred to as 'tags' (an example of synecdoche), though many prefer the term tag strictly in reference to the markup delimiting the start and end of an element.Įlement (and attribute) names may be written in any combination of upper or lower case in HTML, but must be in lower case in XHTML. However, it is quite common to set these with CSS to display as an inline list.

are %block elements and are presented as block elements by default. Note though that this CSS behavior can, and frequently is, changed from the default. Block and inline elements have the appropriate and different CSS behaviors attached to them by default, including the relevance of the box model for particular element types. This behavior cannot be changed it is fixed in the DTD. This is used to define their nesting behavior: block-level elements cannot be placed into an inline context. %block and %inline are groups within the HTML DTD that group elements as being either 'block-level' or 'inline'. HTML also has a similar concept, although different, and the two are very frequently confused. This is applied to those elements that CSS considers to be 'block' elements, set through the CSS display : block declaration. Part of this CSS presentation behavior is the notion of the ' box model'. Once the DOM of elements is obtained, behavior at higher levels of interface (example: screen rendering) is identical or nearly so. HTML as used on the current web is likely to be either treated as XML, by being XHTML, or as HTML5 in either case the parsing of document tags into Document Object Model (DOM) elements is simplified compared to legacy HTML systems. The relation from tags to elements is always that of parsing the actual tags included in the document, without the implied closures that are part of SGML. Although both can use the DTD to specify the supported elements and their permitted combinations as document structure, XML parsing is simpler. XML was developed as a simpler alternative. SGML is complex, which has limited its widespread understanding and adoption. HTML5 creates a similar result by defining what tags can be omitted. (If one paragraph element cannot contain another, any currently open paragraph must be closed before starting another.) Because this implication is based on the combination of the DTD and the individual document, it is not usually possible to infer elements from document tags alone but only by using an SGML-or HTML-aware parser with knowledge of the DTD. But since the DTD states that paragraph elements cannot be nested, an HTML document fragment Para 1 Para 2 Para 3is thus inferred to be equivalent to Para 1 Para 2 Para 3. As a simple example, the tag indicating the start of a paragraph element should be complemented by a tag indicating its end. It is part of general SGML behavior that, where only one valid structure is possible (per the DTD), its explicit statement in any given document is not generally required. it defines the set of element types) and also the valid combinations in which they may appear in a document. The DTD specifies which element types are possible (i.e. Optional tagsĪs HTML (before HTML5) is based on SGML, its parsing also depends on the Document Type Definition (DTD), specifically an HTML DTD (e.g. The contents of the element must be placed between just after the start tag (which might be implied, in certain cases) and just before the end tag (which again, might be implied, in certain cases). (.) The start and end tags of certain normal elements can be omitted, (.)

Tags are used to delimit the start and end of elements in the markup. Similarly the W3C Recommendadtion HTML 5.1 2nd Edition explicitly says: For instance, the HEAD element is always present, even though both start and end HEAD tags may be missing in the markup. Remember that the element is one thing, and the tag (be it start or end tag) is another. Some people refer to elements as tags (e.g., 'the P tag'). The distinction is explicitly emphasised in HTML 4.01 Specification:Įlements are not tags. This is the case for many, but not all, elements within an HTML document. tags Īs is generally understood, the position of an element is indicated as spanning from a start tag and is terminated by an end tag. HTML element content categories Elements vs.

Html cannot be written in a plain text editor.