HTML5的结构和语义(2):结构

【 tulaoshi.com - Web开发 】

　　由于缺少结构，即使是形式良好的 HTML 页面也比较难以处理。必须分析标题的级别，才能看出各个部分的划分方式。边栏、页脚、页眉、导航条、主内容区和各篇文章都由通用的 div 元素来表示。HTML 5 添加了一些新元素，专门用来标识这些常见的结构： 

　· section：这可以是书中的一章或一节，实际上可以是在 HTML 4 中有自己的标题的任何东西
　· header：页面上显示的页眉；与 head 元素不一样
　· footer：页脚；可以显示电子邮件中的签名
　· nav：指向其他页面的一组链接
　· article：blog、杂志、文章汇编等中的一篇文章

　　我们来考虑一个典型的 blog 主页，它的顶部有页眉，底部有页脚，还有几篇文章、一个导航区和一个边栏，见代码1 典型的 blog 页面

html
  head
    titleMokka mit Schlag /title
 /head
body
div id="page"
  div id="header"
    h1a href="http://www.elharo.com/blog"Mokka mit Schlag/a/h1
  /div
  div id="container"
    div id="center" class="column"              
      div class="post" id="post-1000572"
        h2a href=
      "/blog/birding/2007/04/23/spring-comes-and-goes-in-sussex-county/"
      Spring Comes (and Goes) in Sussex County/a/h2
        div class="entry"

          pYesterday I joined the Brooklyn Bird Club for our
          annual trip to Western New Jersey, specifically Hyper
          Humus, a relatively recently discovered hot spot. It
          started out as a nice winter morning when we arrived
          at the site at 7:30 A.M., progressed to Spring around
          10:00 A.M., and reached early summer by 10:15. /p
        /div
      /div
      div class="post" id="post-1000571"
        h2a href=
          "/blog/birding/2007/04/23/but-does-it-count-for-your-life-list/"

           But does it count for your life list？/a/h2
        div class="entry"
          pSeems you can now go a
          href="http://www.wired.com/science/discoveries/news/
          2007/04/cone_sf"bird watching via the Internet/a. I
          haven't been able to test it out yet (20 user
          limit apparently) but this is certainly cool.
          Personally, I can't imagine it replacing
          actually being out in the field by any small amount.
          On the other hand, I've always found it quite

          sad to meet senior birders who are no longer able to
          hold binoculars steady or get to the park. I can
          imagine this might be of some interest to them. At
          least one elderly birder did a big year on TV, after
          he could no longer get out so much. This certainly
          tops that./p
        /div
      /div
      /div
    div class="navigation"
      div class="alignleft"
         a href="/blog/page/2/"« _fcksavedurl=""/blog/page/2/"«" Previous Entries/a
       /div
      div class="alignright"/div
    /div
  /div
  div id="right" class="column"
    ul id="sidebar"
      lih2Info/h2
      ul
        lia href="/blog/comment-policy/"Comment Policy/a/li
        lia href="/blog/todo-list/"Todo List/a/li
      /ul/li
      lih2Archives/h2
        ul
          lia href='/blog/2007/04/'April 2007/a/li

          lia href='/blog/2007/03/'March 2007/a/li
          lia href='/blog/2007/02/'February 2007/a/li
          lia href='/blog/2007/01/'January 2007/a/li
        /ul
      /li
    /ul
  /div
  div id="footer"
    pCopyright 2007 Elliotte Rusty Harold/p
  /div
/div
/body
/html

　　即使有正确的缩进，这些嵌套的 div 仍然让人觉得非常混乱。在 HTML 5 中，可以将这些元素替换为语义性的元素，见代码2 用 HTML5编写的典型blog页面

html
 head
    titleMokka mit Schlag /title
 /head
body
  header
    h1a href="http://www.elharo.com/blog"Mokka mit Schlag/a/h1
  /header
  section              
      article
        h2a href=
        "/blog/birding/2007/04/23/spring-comes-and-goes-in-sussex-county/"
         Spring Comes (and Goes) in Sussex County/a/h2
        pYesterday I joined the Brooklyn Bird Club for our
        annual trip to Western New Jersey, specifically Hyper 
        Humus, a relatively recently discovered hot spot. It
        started out as a nice winter morning when we arrived at
        the site at 7:30 A.M., progressed to Spring around 10:00
        A.M., and reached early summer by 10:15. /p
      /article
      article

          2007/04/cone_sf"bird watching via the Internet/a. I
          haven't been able to test it out yet (20 user
          limit apparently) but this is certainly cool.
          Personally, I can't imagine it replacing
          actually being out in the field by any small amount.
          On the other hand, I've always found it quite
          sad to meet senior birders who are no longer able to
          hold binoculars steady or get to the park. I can
          imagine this might be of some interest to them. At
          least one elderly birder did a big year on TV, after

          he could no longer get out so much. This certainly
          tops that./p
      /article   
    nav
      a href="/blog/page/2/"« _fcksavedurl=""/blog/page/2/"«" Previous Entries/a
    /nav
  /section
  nav
    ul
      lih2Info/h2
      ul
        lia href="/blog/comment-policy/"Comment Policy/a/li
        lia href="/blog/todo-list/"Todo List/a/li
      /ul/li 
      lih2Archives/h2
        ul
          lia href='/blog/2007/04/'April 2007/a/li
          lia href='/blog/2007/03/'March 2007/a/li
          lia href='/blog/2007/02/'February 2007/a/li
          lia href='/blog/2007/01/'January 2007/a/li
        /ul
      /li
    /ul
  /nav
  footer
    pCopyright 2007 Elliotte Rusty Harold/p
  /footer
/body
/html

　　现在不再需要 div 了。不再需要自己设置 class 属性，从标准的元素名就可以推断出各个部分的意义。这对于音频浏览器、手机浏览器和其他非标准浏览器尤其重要。