W3C 发表 HTML 5.1 网页推荐规范

by admin on 2020年4月22日
  1. The accesskey takes a single character as a value (as in HTML 4).

  2. header and footer elements can be nested, if each level is
    within a sectioning element.

  3. option elements can be empty.

  4. The mousewheel event is called wheel.

  5. The value attribute of input type="submit" is translatable.

  6. figcaption can appear anywhere within a figure.

  7. Having title, or writing email to a friend does not make
    an img missing alt conformant.

  8. The content of time is phrasing content, or text.

  9. Blank alt on area elements with duplicate href attributes is
    no longer conformant.

  10. When navigating internally, the next search for a link etc starts
    from where the navigation moved to.

  11. img and related elements support width="0".

  12. .tFoot and .createTFoot() always insert at the end of a table

  13. fieldset and namedItem make HTMLCollections
    not HTMLFormControlsCollections and HTMLOptionsCollections.

  14. frameElement can return null.

  15. For images which don’t resolve currentSrc is the URL given to the
    resolver, not necessarily the absolute URL.

  16. script IDL attributes reflect.

  17. meta refresh allows ; or url= to be optional.

  18. navigator.javaEnabled() is a method.

  19. fileCallback is called blobcallback.

  20. The toBlob() callback is non-nullable.

  21. origin on HTMLHyperlinkElementUtils and Location is readonly.

  22. The first title child of an SVG is its title, not the last.

  23. window.open() can return null

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| Elements


  • List of Elements
    • Document

      • head
      • title
      • base
      • isindex
      • link
      • meta
      • style
  1. appCache.

  2. Media Controllers.

  3. The command API.

  4. The usemap attribute on object.

  5. The accessKeyLabel IDL attribute.

  6. The form attribute is no longer valid for label.

  7. The multiple attribute on input type="range".

  8. hreflang andtype attributes on area.

  9. The use of nested section elements each with an h1 to create an

  10. Special handling of isindex in form submission.

  11. navigator.yieldForStorageUpdates() and the Storage mutex.

  12. Disallow tfoot before tbody.

  13. [Exposed=Window] for
    HTMLHyperLinkElementUtils, [Exposed=Window, Worker] for
    DOMStringMap and IDL Date.

HTML Reference

The HTML5 specification defines the <base> element in 4.2.3 The


  • HTML
  • HTMLElement
  1. The picture and srcset attributes allow responsive image

  2. The details andsummary elements enable authors to provide
    extended information that users can choose whether to read.

  3. The menuitem and type="context" attribute value enable authors
    to add functionality to the browser’s context menu.

  4. The requestAnimationFrame API allows for more efficient animation.

  5. enqueueJob and nextJob help explain Promise resolution in terms
    of microtasks.

  6. The rev attribute for links, primarily to support RDFa (previously
    defined in HTML 4).

  7. HTMLMediaElement and srcObject objects.

  8. Enable cross-origin track and EventSource and cross-origin
    content for ImageBitmap in canvas.

  9. event-source-errorevent-track-error and event-track-load events
    for media fetching.

  10. onrejectionhandled and onunhandledrejection and APIs for
    tracking promise rejection.

  11. HTMLTableCaptionElementHTMLTableSectionElementHTMLTableRowElement,
    for HTML table elements.

  12. history.scrollRestoration to control where a users’ view is
    directed when navigating through their history.

  13. IDL [SameObject], for some objects that return collections.

  14. Add “noopener” to rel and window to allow for browsing contexts
    to be separated.

  15. nonce attribute on script and style to support the use of
    Content Security Policy.


The <base> element allows authors to specify the document base URL
for the purposes of resolving relative URLs, and the name of the default
browsing context for the purposes of following hyperlinks. The element
does not represent any content beyond this information.



  • A base element must have either an href attribute, a target
    attribute, or both.
  • There must be no more than one base element per document.


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HTML Attributes

  • href = valid URL potentially surrounded by spaces
    A base element, if it has an href attribute, must come before any
    other elements in the tree that have attributes defined as taking
    URLs, except the html element (its manifest attribute isn’t affected
    by base elements). [Example

  • target = valid browsing context name or keyword ( _blank, _self,
    _parent, or _top)
    The value of the target attribute is used as the default when
    hyperlinks and forms in the Document cause navigation.

See also global





  • 1 <base>
    • 1.1 Point
    • 1.2 HTML
    • 1.3 Examples
      • 1.3.1 Example
    • 1.4 HTML




Example A

In this example, a <base> element is used to set the document base
The link in the this example would be a link to
“” [try it]:

<!DOCTYPE html>
        <meta charset="utf-8">
        <title>This is an example for the <base> element</title>
        <base href="http://www.example.com/news/index.html">
        <p>Visit the <a href="archives.html">archives</a>.</p>

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