Site Compatibility for Firefox 23




Firefox 23 Aurora (pre-Beta) was released on . While it has been developed to maintain compatibility as much as possible, the new version includes some changes affecting backward compatibility aimed at improving interoperability with the other browsers or following the latest Web standards. Here's the list of such changes — Hope this helps whenever you test your sites or applications.

This article only explains the changes that may affect backward compatibility for Websites. For the other new features and changes, please read the following documents:

This list may be updated until the release of the final version on , so please check back later.


Firefox previously supported the Netscape-derived blink effect with the blink keyword for the CSS text-decoration property as well as the HTML blink element and the DOM String.blink method. Starting with Firefox 23, the blink effect no longer works. While text-decoration:blink continues to be supported by the CSS parser and the DOM APIs, the HTML parser has dropped the blink element support, thus the element will be treated as an unknown element. Internet Explorer, Chrome and Safari haven't supported the effect. Opera may also drop the support once it switches to the Blink rendering engine.



window.sidebar.addPanel and window.sidebar.addPersistentPanel are no longer supported. These methods were a part of a Netscape-derived API which allowed Web publishers to integrate their contents as sidebar panels of the browser. They were not standardized, rarely used, and not very well supported. No other browsers have implemented these.

There is also a plan to remove window.sidebar itself in the future.


requestAnimationFrame, the unprefixed version of mozRequestAnimationFrame, has been added. This unprefixed method passes a DOMHighResTimeStamp to callbacks. It has microsecond precision and can be compared to

On the other hand, the prefixed method, which will be removed in the future, continues to pass an epoch-based DOMTimeStamp to callbacks. The passed-in value has millisecond precision and can be compared to mozAnimationStartTime.


The contentDocument property on frames now returns null if the caller doesn't subsume the document. This change affects the contentDocument property on the frame, iframe and object elements as well as the getSVGDocument method on the embed, iframe and object elements.


The window.defaultStatus property is no longer available. Setting this property has had no effect in Firefox because the default preference has disallowed changes to the status text by Web pages. Recently, the Firefox UI dropped support for enabling that pref. Also, this property is not specified in the HTML5 spec. window.status is still available.


The support for obsolete document.createEvent("AnimationEvent"), document.createEvent("TransitionEvent"), AnimationEvent.initAnimationEvent, and TransitionEvent.initTransitionEvent has been removed.


Audio Data API被废弃

The non-standard, experimental Audio Data API is now considered deprecated. The standard Web Audio API can be used instead.


The HTMLMediaElement.initialTime property is no longer available, due to the removal from the spec.



Firefox 18 introduced preferences to block loading content from non-SSL (http) sites on SSL (https) pages. One of those preferences, security.mixed_content.block_active_content is now enabled by default in order to enhance user security. That means insecure scripts, stylesheets, plug-in contents, inline frames, Web fonts and WebSockets are blocked on secure pages, and a notification is displayed instead. It will not block "display content" like images, videos or audio. See Tanvi Vyas' blog post for details.

Mozilla is tracking mixed content issues found on major sites as well as its own properties.