---
title: Firefox 23 for developers
slug: Mozilla/Firefox/Releases/23
tags:
  - Firefox
  - Firefox 23
translation_of: Mozilla/Firefox/Releases/23
---
<div>{{FirefoxSidebar}}</div><h2 id="Web开发者需要注意的变化">Web开发者需要注意的变化</h2>

<h3 id="HTML">HTML</h3>

<ul>
 <li>Mixed content blocking. Firefox will no longer load non-secure (http) resources on secure (https) pages ({{bug(834836)}}).</li>
 <li>The standard syntax of <a href="https://developer.mozilla.org/en-US/docs/Security/CSP" title="/en-US/docs/Security/CSP">CSP</a> 1.0 policies are now implemented and enforced by default.</li>
</ul>

<h3 id="JavaScript">JavaScript</h3>

<p> </p>

<ul>
 <li>The <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty" title="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty"><code>Object.defineProperty</code></a> method can now be used to redefine the <code>length</code>property of an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" title="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array"><code>Array</code></a> object.</li>
 <li>The option to disable JavaScript, including the options to allow moving windows/replace context menu, have been removed. You may still disable JavaScript by double clicking the "javascript.enabled" option in about:config.</li>
</ul>

<h3 id="HTML_2">HTML</h3>

<ul>
 <li>The {{HTMLElement("blink")}} element support is now completely dropped. The <code>&lt;blink&gt;</code> tag now implements the {{domxref("HTMLUnknownElement")}} interface ({{bug(857820)}}).</li>
 <li>The <code>range</code> type of the {{HTMLElement("input")}} element (<code><a href="https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/range">&lt;input type="range"&gt;</a></code>) has been switched on by default ({{bug(841950)}}).</li>
</ul>

<p> </p>

<h3 id="DOM">DOM</h3>

<ul>
 <li>D3E <a href="/en-US/docs/DOM/KeyboardEvent#Key_names_and_Char_values" title="/en-US/docs/DOM/KeyboardEvent#Key_names_and_Char_values"><code>KeyboardEvent.key</code></a> 现在只支持不可打印字符所在的键({{bug(842927)}}).</li>
 <li>{{domxref("DOMImplementation.createHTMLDocument")}}方法的<code>title参数成为可选的</code>(根据最新规范).</li>
 <li>The ability to add a sidebar panel (<code>window.sidebar.addPanel</code>) has been dropped ({{bug(691647)}}).</li>
 <li>The unprefixed {{domxref("Window.requestAnimationFrame")}} and {{domxref("Window.cancelAnimationFrame")}} methods has been added ({{bug(704063)}}). The unprefixed {{domxref("Window.requestAnimationFrame")}} receives a {{domxref("DOMHighResTimeStamp")}} as argument; the prefixed version did, and still is, received a {{domxref("DOMTimeStamp")}}({{bug(753453)}}).</li>
 <li>The text argument for {{domxref("window.alert")}} and {{domxref("window.confirm")}} is now optional ({{bug(861605)}}).</li>
 <li>The {{domxref("HTMLMediaElement.initialTime")}} property, removed from the spec, is no more supported ({{bug(742537)}}).</li>
 <li>The {{domxref("AnimationEvent.AnimationEvent", "AnimationEvent()")}} constructor has been added ({{bug(848293)}}).</li>
 <li>The {{domxref("AnimationEvent.pseudoElement")}} property has been implemented ({{bug(848293)}}).</li>
 <li>The {{domxref("TransitionEvent.TransitionEvent", "TransitionEvent()")}} constructor has been added ({{bug(848291)}}).</li>
 <li>The {{domxref("TransitionEvent.pseudoElement")}} property has been implemented ({{bug(848291)}}).</li>
 <li>The non-standard {{domxref("TransitionEvent.initTransitionEvent()")}} and {{domxref("AnimationEvent.initAnimationEvent()")}} have been removed ({{bug(868751)}}).</li>
</ul>

<h3 id="CSS">CSS</h3>

<ul>
 <li>CSS属性<code><a href="/en-US/docs/CSS/text-decoration" title="/en-US/docs/CSS/text-decoration">text-decoration</a>: blink;带来的闪烁效果被删除</code>({{bug(857820)}}).</li>
 <li>In-flow {{cssxref("::after")}} and {{cssxref("::before")}} pseudo-elements are now flex items ({{bug(867454)}}).</li>
 <li>The way to compute <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/length#Viewport-percentage_lengths">viewport units</a> has been changed. In conjunction with <code>overflow:auto</code>, space taken by eventual scrollbars is not substracted from the viewport, whereas in the case of <code>overflow:scroll</code>, it is. ({{bug(811403)}})</li>
</ul>

<h3 id="WebRTC">WebRTC</h3>

<ul>
 <li>Instead of including usernames in the {{domxref("RTCIceServer.url")}} property (such as stun:username@stunserver.example.com), you now need to use the new {{domxref("RTCIceServer.username")}} property.</li>
</ul>

<h3 id="MathML">MathML</h3>

<ul>
 <li>{{MathMLElement("mspace")}}元素开始支持负数宽度 ({{bug(717546)}}).</li>
 <li>The {{MathMLElement("semantics")}} element now determines the visible child as described in the MathML3 specification.</li>
</ul>

<h2 id="Changes_for_addon_and_Mozilla_developers">Changes for addon and Mozilla developers</h2>

<h3 id="Firefox_developer_tools">Firefox developer tools</h3>

<p>Addons that overlay chrome://browser/content/debugger.xul must now overlay chrome://browser/content/devtools/debugger.xul. You may add references to both these files in chrome.manifest for compatibility.</p>

<p> </p>

<h2 id="See_also">See also</h2>

<ul>
 <li><a href="http://www.mozilla.org/en-US/firefox/23.0a2/auroranotes/">Firefox 23 Aurora Notes</a></li>
 <li><a href="https://www.fxsitecompat.com/en-US/versions/23/">Site Compatibility for Firefox 23</a></li>
</ul>

<p> </p>

<p> </p>

<h3 id="之前版本">之前版本</h3>

<p>{{Firefox_for_developers('22')}}</p>