html5, Web3.0时代的网页编程！
HTML5是最新一代HTML标记语言的修订版本，目前已经正式发布，备受各界关注。
之所以被广泛关注，是因为其目标是提供html语言对于图像，语音，视频等信息的原生支持，
以减少网页浏览器对于各种插件的依赖，满足人们日益增长的对于“富网络”应用的浏览需求。
HTML5添加了许多新的语法标签，例如像<article>，<header>，<nav>，<section>，
<audio>，<video>和<canvas>等的元素，并还集成了部分SVG的内容。
同时，HTML5去除了一些陈旧的语法标签，像<a>，<p>，<center>，<font>，<cite>和<menu>等，
使得文档的数据内容和文档的数据逻辑更加的清晰，更加的便于搜索。
-- html5标签描述 --
<!--...--> Defines a comment 语句注释
<!DOCTYPE> Defines the document type 文档类型声明
<a> Defines a hyperlink 超链接
<abbr> Defines an abbreviation 缩写
<acronym> Not supported in HTML5
<address> Defines contact information for the author/owner of a document/article 文档作者的联系信息
<applet> Not supported in HTML5
<area> Defines an area inside an image-map 地图图像的呈现区域
<article> New Defines an article 新定义一篇文章
<aside> New Defines content aside from the page content
<audio> New Defines sound content
<b> Defines bold text
<base> Specifies the base URL/target for all relative URLs in a document
<basefont> Not supported in HTML5
<bdi> New Isolates a part of text that might be formatted in a different direction from other text outside it
<bdo> Overrides the current text direction
<big> Not supported in HTML5
<blockquote> Defines a section that is quoted from another source
<body> Defines the document's body
<br> Defines a single line break
<button> Defines a clickable button
<canvas> New Used to draw graphics, on the fly, via scripting (usually JavaScript)
<caption> Defines a table caption
<center> Not supported in HTML5
<cite> Defines the title of a work
<code> Defines a piece of computer code
<col> Specifies column properties for each column within a <colgroup> element
<colgroup> Specifies a group of one or more columns in a table for formatting
<command> New Defines a command button that a user can invoke
<datalist> New Specifies a list of pre-defined options for input controls
<dd> Defines a description of an item in a definition list
<del> Defines a text that has been deleted from a document
<details> New Defines additional details that the user can view or hide
<dfn> Defines a definition term
<dir> Not supported in HTML5
<div> Defines a section in a document
<dl> Defines a definition list
<dt> Defines a term (an item) in a definition list
<em> Defines emphasized text
<embed> New Defines a container for an external application or interactive content (a plug-in)
<fieldset> Groups related elements in a form
<figcaption> New Defines a caption for a <figure> element
<figure> New Specifies self-contained content
<font> Not supported in HTML5
<footer> New Defines a footer for a document or section
<form> Defines an HTML form for user input
<frame> Not supported in HTML5
<frameset> Not supported in HTML5
<h1> to <h6> Defines HTML headings
<head> Defines information about the document
<header> New Specifies an introduction, or a group of navigation elements for a document
<hgroup> New Groups a set of <h1> to <h6> elements when a heading has multiple levels
<hr> Defines a thematic change in the content
<html> Defines the root of an HTML document
<i> Defines a part of text in an alternate voice or mood
<iframe> Defines an inline frame
<img> Defines an image
<input> Defines an input control
<ins> Defines a text that has been inserted into a document
<keygen> New Defines a key-pair generator field (for forms)
<kbd> Defines keyboard input
<label> Defines a label for an input element
<legend> Defines a caption for a <fieldset>, <figure>, or <details> element
<li> Defines a list item
<link> Defines the relationship between a document and an external resource (most used to link to style sheets)
<map> Defines a client-side image-map
<mark> New Defines marked/highlighted text
<menu> Defines a list/menu of commands
<meta> Defines metadata about an HTML document
<meter> New Defines a scalar measurement within a known range (a gauge)
<nav> New Defines navigation links
<noframes> Not supported in HTML5
<noscript> Defines an alternate content for users that do not support client-side scripts
<object> Defines an embedded object
<ol> Defines an ordered list
<optgroup> Defines a group of related options in a drop-down list
<option> Defines an option in a drop-down list
<output> New Defines the result of a calculation
<p> Defines a paragraph
<param> Defines a parameter for an object
<pre> Defines preformatted text
<progress> New Represents the progress of a task
<q> Defines a short quotation
<rp> New Defines what to show in browsers that do not support ruby annotations
<rt> New Defines an explanation/pronunciation of characters (for East Asian typography)
<ruby> New Defines a ruby annotation (for East Asian typography)
<s> Defines text that is no longer correct
<samp> Defines sample output from a computer program
<script> Defines a client-side script
<section> New Defines a section in a document
<select> Defines a drop-down list
<small> Defines smaller text
<source> New Defines multiple media resources for media elements (<video> and <audio>)
<span> Defines a section in a document
<strike> Not supported in HTML5
<strong> Defines important text
<style> Defines style information for a document
<sub> Defines subscripted text
<summary> New Defines a visible heading for a <details> element
<sup> Defines superscripted text
<table> Defines a table
<tbody> Groups the body content in a table
<td> Defines a cell in a table
<textarea> Defines a multiline input control (text area)
<tfoot> Groups the footer content in a table
<th> Defines a header cell in a table
<thead> Groups the header content in a table
<time> New Defines a date/time
<title> Defines a title for the document
<tr> Defines a row in a table
<track> New Defines text tracks for media elements (<video> and <audio>)
<tt> Not supported in HTML5
<u> Not supported in HTML5
<ul> Defines an unordered list
<var> Defines a variable
<video> New Defines a video or movie
<wbr> New Defines a possible line-break