HTML5和HTML4的不同英文.docx

1、HTML5 和和 HTML4 的不同英文的不同英文 Abstract HTML5 defines the fifth major revision of the core language of the World Wide Web,HTML.HTML5 differences from HTML4 describes the differences between HTML4 and HTML5 and provides some of the rationale for the changes.This document may not provide accurate informati

2、on as the HTML5 specification is still actively in development.When in doubt,always check the HTML5 specification itself.HTML5 Status of this Document This section describes the status of this document at the time of its publication.Other documents may supersede this document.A list of current W3C p

3、ublications and the latest revision of this technical report can be found in the W3C technical reports index at http:/www.w3.org/TR/.This is the 13 January 2011 W3C Working Draft produced by the HTML Working Group,part of the HTML Activity.The Working Group intends to publish this document as a Work

4、ing Group Note to accompany the HTML5 specification.The appropriate forum for comments is public-html-commentsw3.org,a mailing list with a public archive.Publication as a Working Draft does not imply endorsement by the W3C Membership.This is a draft document and may be updated,replaced or obsoleted

5、by other documents at any time.It is inappropriate to cite this document as other than work in progress.This document was produced by a group operating under the 5 February 2004 W3C Patent Policy.W3C maintains a public list of any patent disclosures made in connection with the deliverables of the gr

6、oup;that page also includes instructions for disclosing a patent.An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s)must disclose the information in accordance with section 6 of the W3C Patent Policy.Table of Contents 1.Introduction o 1.1.Open

7、 Issues o 1.2.Backwards Compatible o 1.3.Development Model 2.Syntax o 2.1.Character Encoding o 2.2.The DOCTYPE o 2.3.MathML and SVG o 2.4.Miscellaneous 3.Language o 3.1.New Elements o 3.2.New Attributes o 3.3.Changed Elements o 3.4.Changed attributes o 3.5.Absent Elements o 3.6.Absent Attributes 4.A

8、PIs o 4.1.Extensions to HTMLDocument o 4.2.Extensions to HTMLElement 5.HTML5 Changelogs o 5.1.Changes since 19 October 2010 o 5.2.Changes from 24 June 2010 to 19 October 2010 o 5.3.Changes from 4 March 2010 to 24 June 2010 o 5.4.Changes from 25 August 2009 to 4 March 2010 o 5.5.Changes from 23 April

9、 2009 to 25 August 2009 o 5.6.Changes from 12 February 2009 to 23 April 2009 o 5.7.Changes from 10 June 2008 to 12 February 2009 o 5.8.Changes from 22 January 2008 to 10 June 2008 Acknowledgments References 1.Introduction HTML has been in continuous evolution since it was introduced to the Internet

10、in the early 1990s.Some features were introduced in specifications;others were introduced in software releases.In some respects,implementations and author practices have converged with each other and with specifications and standards,but in other ways,they continue to diverge.HTML4 became a W3C Reco

11、mmendation in 1997.While it continues to serve as a rough guide to many of the core features of HTML,it does not provide enough information to build implementations that interoperate with each other and,more importantly,with a critical mass of deployed content.The same goes for XHTML1,which defines

12、an XML serialization for HTML4,and DOM Level 2 HTML,which defines JavaScript APIs for both HTML and XHTML.HTML5 will replace these documents.DOM2HTML HTML4 XHTML1 The HTML5 draft reflects an effort,started in 2004,to study contemporary HTML implementations and deployed content.The draft:1.Defines a

13、single language called HTML5 which can be written in HTML syntax and in XML syntax.2.Defines detailed processing models to foster interoperable implementations.3.Improves markup for documents.4.Introduces markup and APIs for emerging idioms,such as Web applications.1.1.Open Issues HTML5 is still a d

14、raft.The contents of HTML5,as well as the contents of this document which depend on HTML5,are still being discussed on the HTML Working Group and WHATWG mailing lists.The open issues are linked from the HTML5 draft.1.2.Backwards Compatible HTML5 is defined in a way that it is backwards compatible wi

15、th the way user agents handle deployed content.To keep the authoring language relatively simple for authors several elements and attributes are not included as outlined in the other sections of this document,such as presentational elements that are better dealt with using CSS.User agents,however,wil

16、l always have to support these older elements and attributes and this is why the HTML5 specification clearly separates requirements for authors and user agents.For instance,this means that authors cannot use the isindex or the plaintext element,but user agents are required to support them in a way t

17、hat is compatible with how these elements need to behave for compatibility with deployed content.Since HTML5 has separate conformance requirements for authors and user agents there is no longer a need for marking features deprecated.1.3.Development Model The HTML5 specification will not be considere

18、d finished before there are at least two complete implementations of the specification.A test suite will be used to measure completeness of the implementations.This approach differs from previous versions of HTML,where the final specification would typically be approved by a committee before being a

19、ctually implemented.The goal of this change is to ensure that the specification is implementable,and usable by authors once it is finished.2.Syntax 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 f

20、eatures 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 lar

21、gely 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:Example document Example paragraph HTML5 also defines a text/html-sandboxed media type for documents using the H

22、TML 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/1

23、999/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.Example document Example paragraph 2.1.

24、Character Encoding For the HTML syntax of HTML5,authors have three means of setting the character encoding:At the transport level.By using the HTTP Content-Type header for instance.Using a Unicode Byte Order Mark(BOM)character at the start of the file.This character provides a signature for the enco

25、ding used.Using a meta element with a charset attribute that specifies the encoding within the first 512 bytes of the document.E.g.could be used to specify the UTF-8 encoding.This replaces the need for although that syntax is still allowed.For the XML syntax,authors have to use the rules as set fort

26、h in the XML specifications to set 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

27、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

28、 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 loo

29、k like:SVG in text/html A green circle: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.2.4.Miscellaneous There are a few other syntax changes worthy of mentioning:HTML now has nati

30、ve support for IRIs,though they can only be fully used if the document encoding is UTF-8 or UTF-16.The lang attribute takes the empty string in addition to a valid language identifier,just like xml:lang does in XML.3.Language This section is split up in several subsections to more clearly illustrate

31、 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:section represents a

32、 generic document or application section.It can be used together with the h1,h2,h3,h4,h5,and h6 elements to indicate the document structure.article represents an independent piece of content of a document,such as a blog entry or newspaper article.aside represents a piece of content that is only slig

33、htly related to the rest of the page.hgroup represents the header of a section.header represents a group of introductory or navigational aids.footer represents a footer for a section and can contain information about the author,copyright information,et cetera.nav represents a section of the document intended for navigation.figure represents a piece of self-contained flow content,typically referenc