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Changes / New in HTML5

in Deutsch: Änderungen in>HTML5

2. Syntax of HTML5

HTML5 defines an HTML syntax that is compatible with HTML4 and XHTML1 documents published on the Web, but is not compatible with the more esoteric SGML features of HTML4, such as processing instructions and shorthand markup as these are not supported by most user agents. Documents using the HTML syntax are almost always served with the text/html media type. HTML5 also defines detailed parsing rules (including "error handling") for this syntax which are largely compatible with popular implementations. User agents must use these rules for resources that have the text/html media type. Here is an example document that conforms to the HTML syntax: HTML5 also defines a text/html-sandboxed media type for documents using the HTML syntax. This can be used when hosting untrusted content. The other syntax that can be used for HTML5 is XML. This syntax is compatible with XHTML1 documents and implementations. Documents using this syntax need to be served with an XML media type and elements need to be put in the http://www.w3.org/1999/xhtml namespace following the rules set forth by the XML specifications. [XML] Below is an example document that conforms to the XML syntax of HTML5. Note that XML documents must be served with an XML media type such as application/xhtml+xml or application/xml.

2.1. Character Encoding For the HTML syntax of HTML5, authors have three means of setting the character encoding:

2.2. The DOCTYPE The HTML syntax of HTML5 requires a DOCTYPE to be specified to ensure that the browser renders the page in standards mode. The DOCTYPE has no other purpose and is therefore optional for XML. Documents with an XML media type are always handled in standards mode. [DOCTYPE] The DOCTYPE declaration is and is case-insensitive in the HTML syntax. DOCTYPEs from earlier versions of HTML were longer because the HTML language was SGML-based and therefore required a reference to a DTD. With HTML5 this is no longer the case and the DOCTYPE is only needed to enable standards mode for documents written using the HTML syntax. Browsers already do this for .

2.3. MathML and SVG The HTML syntax of HTML5 allows for MathML and SVG elements to be used inside a document. E.g. a very simple document using some of the minimal syntax features could look like: More complex combinations are also possible. E.g. with the SVG foreignObject element you could nest MathML, HTML, or both inside an SVG fragment that is itself inside HTML.

 

3. Language of HTML5

This section is split up in several subsections to more clearly illustrate the various differences there are between HTML4 and HTML5.

3.1. New Elements The links in this section may stop working if elements are renamed and/or removed. They should function in the latest version of this draft. The following elements have been introduced for better structure:

3.2. New Attributes HTML5 has introduced several new attributes to various elements that were already part of HTML4:

  • The a and area elements now have a media attribute for consistency with the link element.
  • The a and area elements have a new attribute called ping that specifies a space-separated list of URLs which have to be pinged when the hyperlink is followed. Currently user tracking is mostly done through redirects. This attribute allows the user agent to inform users which URLs are going to be pinged as well as giving privacy-conscious users a way to turn it off.
  • The area element, for consistency with the a and link elements, now also has the hreflang and rel attributes.
  • The base element can now have a target attribute as well, mainly for consistency with the a element. (This is already widely supported.) Also, the target attribute for the a and area elements is no longer deprecated, as it is useful in Web applications, e.g. in conjunction with iframe.
  • The value attribute for the li element is no longer deprecated as it is not presentational. The same goes for the start attribute of the ol element.
  • The meta element has a charset attribute now as this was already widely supported and provides a nice way to specify the character encoding for the document.
  • A new autofocus attribute can be specified on the input (except when the type attribute is hidden), select, textarea and button elements. It provides a declarative way to focus a form control during page load. Using this feature should enhance the user experience as the user can turn it off if the user does not like it, for instance.
  • A new placeholder attribute can be specified on the input and textarea elements. It represents a hint intended to aid the user with data entry.
  • The new form attribute for input, output, select, textarea, button and fieldset elements allows for controls to be associated with a form. I.e. these elements can now be placed anywhere on a page, not just as descendants of the form element.
  • The new required attribute applies to input (except when the type attribute is hidden, image or some button type such as submit) and textarea. It indicates that the user has to fill in a value in order to submit the form.
  • The fieldset element now allows the disabled attribute disabling all its contents when specified.
  • The input element has several new attributes to specify constraints: autocomplete, min, max, multiple, pattern and step. As mentioned before it also has a new list attribute which can be used together with the datalist element.
  • The form element has a novalidate attribute that can be used to disable form validation submission (i.e. the form can always be submitted).
  • The input and button elements have formaction, formenctype, formmethod, formnovalidate, and formtarget as new attributes. If present, they override the action, enctype, method, novalidate, and target attributes on the form element.
  • The menu element has two new attributes: type and label. They allow the element to transform into a menu as found in typical user interfaces as well as providing for context menus in conjunction with the global contextmenu attribute.
  • The style element has a new scoped attribute which can be used to enable scoped style sheets. Style rules within such a style element only apply to the local tree.
  • The script element has a new attribute called async that influences script loading and execution.
  • The html element has a new attribute called manifest that points to an application cache manifest used in conjunction with the API for offline Web applications.
  • The link element has a new attribute called sizes. It can be used in conjunction with the icon relationship (set through the rel attribute) to indicate the size of the referenced icon.
  • The ol element has a new attribute called reversed to indicate that the list order is descending when present.
  • The iframe element has three new attributes called sandbox, seamless, and srcdoc which allow for sandboxing content, e.g. blog comments. Several attributes from HTML4 now apply to all elements. These are called global attributes: class, dir, id, lang, style, tabindex and title. There are also several new global attributes:
  • The contenteditable attribute indicates that the element is an editable area. The user can change the contents of the element and manipulate the markup.
  • The contextmenu attribute can be used to point to a context menu provided by the author.
  • The data-
  • collection of author-defined attributes. Authors can define any attribute they want as long as they prefix it with data- to avoid clashes with future versions of HTML. The only requirement on these attributes is that they are not used for user agent extensions.
  • The draggable attribute can be used together with the new drag & drop API.
  • The hidden attribute indicates that an element is not yet, or is no longer, relevant.
  • The role and aria-
  • collection attributes which can be used to instruct assistive technology.
  • The spellcheck attribute allows for hinting whether content can be checked for spelling or not. HTML5 also makes all event handler attributes from HTML4, which take the form onevent-name, global attributes and adds several new event handler attributes for new events it defines. E.g. the play event which is used by the API for the media elements (video and audio).

    3.3. Changed Elements These elements have slightly modified meanings in HTML5 to better reflect how they are used on the Web or to make them more useful:

  • The a element without an href attribute now represents a "placeholder link". It can also contain flow content rather than being restricted to phrase content.
  • The address element is now scoped by the new concept of sectioning.
  • The b element now represents a span of text to be stylistically offset from the normal prose without conveying any extra importance, such as keywords in a document abstract, product names in a review, or other spans of text whose typical typographic presentation is emboldened.
  • The cite element now solely represents the title of a work (e.g. a book, a paper, an essay, a poem, a score, a song, a script, a film, a TV show, a game, a sculpture, a painting, a theatre production, a play, an opera, a musical, an exhibition, a legal case report, etc). Specifically the example in HTML4 where it is used to mark up the name of a person is no longer considered conforming.
  • The hr element now represents a paragraph-level thematic break.
  • The i element now represents a span of text in an alternate voice or mood, or otherwise offset from the normal prose, such as a taxonomic designation, a technical term, an idiomatic phrase from another language, a thought, a ship name, or some other prose whose typical typographic presentation is italicized. Usage varies widely by language.
  • For the label element the browser should no longer move focus from the label to the control unless such behavior is standard for the underlying platform user interface.
  • The menu element is redefined to be useful for toolbars and context menus.
  • The small element now represents small print (for side comments and legal print).
  • The strong element now represents importance rather than strong emphasis.

    3.4. Changed attributes The following attributes are allowed but authors are discouraged from using them and instead strongly encouraged to use an alternative solution:

  • The border attribute on img. It is required to have the value "0" when present. Authors can use CSS instead.
  • The language attribute on script. It is required to have the value "JavaScript" (case-insensitive) when present and cannot conflict with the type attribute. Authors can simply omit it as it has no useful function.
  • The name attribute on a. Authors can use the id attribute instead.
  • The summary attribute on table. The HTML5 draft defines several alternative solutions. 3.5. Absent Elements The elements in this section are not to be used by authors. User agents will still have to support them and various sections in HTML5 define how. E.g. the obsolete isindex element is handled by the parser section. The following elements are not in HTML5 because their effect is purely presentational and their function is better handled by CSS:
  • basefont
  • big
  • center
  • font
  • s
  • strike
  • tt
  • u The following elements are not in HTML5 because their usage affected usability and accessibility for the end user in a negative way:
  • frame
  • frameset
  • noframes The following elements are not included because they have not been used often, created confusion, or their function can be handled by other elements:
  • acronym is not included because it has created a lot of confusion. Authors are to use abbr for abbreviations.
  • applet has been obsoleted in favor of object.
  • isindex usage can be replaced by usage of form controls.
  • dir has been obsoleted in favor of ul. Finally the noscript element is only conforming in the HTML syntax. It is not included in the XML syntax as its usage relies on an HTML parser.

    3.6. Absent Attributes Some attributes from HTML4 are no longer allowed in HTML5. If they need to have any impact on user agents for compatibility reasons it is defined how they should work in those scenarios.

  • rev and charset attributes on link and a.
  • shape and coords attributes on a.
  • longdesc attribute on img and iframe.
  • target attribute on link.
  • nohref attribute on area.
  • profile attribute on head.
  • version attribute on html.
  • name attribute on img (use id instead).
  • scheme attribute on meta.
  • archive, classid, codebase, codetype, declare and standby attributes on object.
  • valuetype and type attributes on param.
  • axis and abbr attributes on td and th.
  • scope attribute on td. In addition, HTML5 has none of the presentational attributes that were in HTML4 as their functions are better handled by CSS:
  • align attribute on caption, iframe, img, input, object, legend, table, hr, div, h1, h2, h3, h4, h5, h6, p, col, colgroup, tbody, td, tfoot, th, thead and tr.
  • alink, link, text and vlink attributes on body.
  • background attribute on body.
  • bgcolor attribute on table, tr, td, th and body.
  • border attribute on table and object.
  • cellpadding and cellspacing attributes on table.
  • char and charoff attributes on col, colgroup, tbody, td, tfoot, th, thead and tr.
  • clear attribute on br.
  • compact attribute on dl, menu, ol and ul.
  • frame attribute on table.
  • frameborder attribute on iframe.
  • height attribute on td and th.
  • hspace and vspace attributes on img and object.
  • marginheight and marginwidth attributes on iframe.
  • noshade attribute on hr.
  • nowrap attribute on td and th.
  • rules attribute on table.
  • scrolling attribute on iframe.
  • size attribute on hr.
  • type attribute on li, ol and ul.
  • valign attribute on col, colgroup, tbody, td, tfoot, th, thead and tr.
  • width attribute on hr, table, td, th, col, colgroup and pre.

    4. APIs

    HTML5 introduces a number of APIs that help in creating Web applications. These can be used together with the new elements introduced for applications:

  • API for playing of video and audio which can be used with the new video and audio elements.
  • An API that enables offline Web applications.
  • An API that allows a Web application to register itself for certain protocols or media types.
  • Editing API in combination with a new global contenteditable attribute.
  • Drag & drop API in combination with a draggable attribute.
  • API that exposes the history and allows pages to add to it to prevent breaking the back button.

    4.1. Extensions to HTMLDocument HTML5 has extended the HTMLDocument interface from DOM Level 2 HTML in a number of ways. The interface is now implemented on all objects implementing the Document interface so it stays meaningful in a compound document context. It also has several noteworthy new members:

  • getElementsByClassName() to select elements by their class name. The way this method is defined will allow it to work for any content with class attributes and a Document object such as SVG and MathML.
  • innerHTML as an easy way to parse and serialize an HTML or XML document. This attribute was previously only available on HTMLElement in Web browsers and not part of any standard.
  • activeElement and hasFocus to determine which element is currently focused and whether the Document has focus respectively.
  • getSelection() which returns an object that represents the current selection(s).

    4.2. Extensions to HTMLElement The HTMLElement interface has also gained several extensions in HTML5:

  • getElementsByClassName() which is basically a scoped version of the one found on HTMLDocument.
  • innerHTML as found in Web browsers today. It is also defined to work in XML context (when it is used in an XML document).
  • classList is a convenient accessor for className. The object it returns, exposes methods (contains(), add(), remove(), and toggle()) for manipulating the element's classes. The a, area and link elements have a similar attribute called relList that provides the same functionality for the rel attribute.