What's New in Deer Park Alpha

This page is based largely on https://www.squarefree.com/burningedg...eases/ (thanks Jesse).

New Web Developer Features


Elements with tabindex="-1" should be focusable

Elements with a negative tabIndex attribute can now have focus, even though they are not in the tab order.

Object should submit

In accordance with the HTML4 specification, <object> elements can now be submitted as part of a form.


CSS2 quotes nesting

Starting with this release, the quotes CSS2 property is fully supported, with the correct quote (depending on the nesting level) used for open-quote and close-quote.

CSS3 :only-child

This CSS3 selector allows selecting an element that has no other elements as siblings in the DOM.

CSS3 columns

An experimental implementation of the proposed CSS3 multicolumn layout draft. This allows easily doing newspaper-like multicolumn presentation.

CSS3 overflow-x and overflow-y properties

These properties can be used to control the overflow behavior in the horizontal and vertical directions somewhat independently. For example, overflow in the horizontal direction could be hidden while overflow in the vertical direction can be scrolled to.

CSS3 cursors

More mouse cursor names are now supported.

URI values on CSS cursor properties

On Windows, OS/2 and Linux (Gtk+ 2.x) one can now use an arbitrary image as the mouse cursor while a given DOM node is being hovered. Any image format supported by Gecko can be used for the image. (SVG, animated GIF, and ANI cursors are not supported.) See cursor for a description of the feature.


CSS outlines can now have rounded corners.

CSS outline property

CSS outlines can now be used. These differ from borders in that they don't affect the page layout.

Counters in CSS-generated content

CSS2 counters are now completely supported (the implementation doesn't match the current CSS2.1 draft, but matches the upcoming one). This allows automatic numbering of sections, headings, and so forth via stylesheets.

JavaScript and DOM

Array extras

New methods have been added to the Array object to facilitate common tasks. See JavaScript 1.5 Array Object.


Text written in new documents created with document.open("text/plain") is now treated as text rather than HTML, so line breaks will remain intact and tags will not be parsed.

XML Events

"XML Events" is a W3C specification to provide XML languages with the ability to integrate declarative event listeners and event handlers.

Cancelling keydown

Cancelling the keydown event now properly cancels any corresponding keyup/keypress events, per the DOM specification.

Accessibility APIs for DHTML

Mozilla now allows DHTML authors to add role and state semantics to custom elements, and exposes that information via MSAA and ATK.

DHTML Performance Fixes

A number of changes were made to significantly improve DHTML speed and smoothness.


SVG Support

SVG is W3C specification providing resolution-independent scalable vector graphics, along with a DOM. A technology preview of native SVG support is included in this release. Currently a subset of SVG 1.1 Full, missing functionality includes filters, declarative animation, and SVG defined fonts.

<canvas> Support

<canvas> is a scriptable drawing surface for dynamically creating bitmap graphics. For a further introduction, see Drawing Graphics with Canvas.


Support HTTP/1.1 408 response code

A persistent connection is now correctly closed when a 408 response code (Request timeout) is received. The request is retried in a new connection.

URIs always sent as UTF8

URIs are now always sent to the server as UTF8, regardless of the linking page's encoding. This fixes images and links on sites with non-ASCII filenames.

XForms support

The W3C's XML Forms language allows writing complex forms in XML, and includes features that regular HTML forms do not have, such as client side validation against XML Schema and XML submission/retrieval. Support for XForms comes as an extension, see Mozilla XForms Project Page.

New Extension Developer Features

Hidden referrer column for history

Extensions can now access the referer information for pages stored in the browser history. This feature can be used to provide alternate history views and other useful functionality. Firefox bug 128398

API for prioritizing HTTP connections

The Mozilla networking library now supports the prioritization of connections to a specific server using nsISupportsPriority. Firefox bug 278531

API for managing user and UA stylesheets

Extensions can now register stylesheet URIs as additional user and UA stylesheets. This means extensions no longer have to try to edit userContent.css to add styling (say for XBL binding attachment) to web pages. See Using the Stylesheet Service.

API for configuring proxies

It is now possible for extensions to easily override the proxy configuration without affecting user-visible preferences. See nsIProtocolProxyService, nsIProtocolProxyFilter, and nsIProtocolProxyCallback. Firefox bug 282442

Dynamic Overlays

Loading of XUL overlays after the document has been displayed is now supported. See nsIDOMXULDocument. Firefox bug 282103

ECMAScript for XML (E4X)

The Mozilla JavaScript engine now supports ECMAScript for XML (E4X), a draft ECMA standard that adds native XML datatypes to the language and provides operators for common XML operations. See the ECMA specification. Firefox bug 246441

Translucent Windows (Windows/Linux)

On Windows and Linux, XUL windows with a transparent background are now supported. This allows whatever is below the window to shine through the window background.

Adding tokens to the User-Agent string

It is now possible for applications, extensions, and vendors to all add tokens to the User-Agent string (using default preferences) without overwriting each other. See documentation. Firefox bug 274928

Toolkit chrome registry

Chrome registration has been significantly improved to use simple plaintext chrome registration manifests, and no longer keeps the chrome.rdf/overlayinfo cache. See Chrome Registration.

Extension Manager

Following are the new features:

  • It is now possible to have Extensions outside the profile and application Extensions directories.
  • Installing extensions can now be done by dropping an XPI into the profile or application Extensions directory.
  • Uninstalling an Extension now involves deleting its folder from the profile or application Extensions directory.
New Preferences bindings

These new bindings make it easier to create preferences windows for extensions. The new preferences windows support instant-apply behavior, which is enabled by default on Mac and Linux.

API for implementing new command-line switches

An API has been introduced so that extensions can easily handle complex command-line flags. This API will be stable and frozen for 1.1. See the interfaces nsICommandLine and nsICommandLineHandler.

XTF Support

The eXtensible Tag Framework allows adding support for new namespaces using XPCOM components to Mozilla (written in JavaScript or C++). See XTF Home Page.

New Browser Features

Improved Preferences

Instant Apply behavior on Linux and Mac

Changes made in the Preferences window now apply immediately, in line with typical behavior in other Mac OS X and GNOME applications. This changes conforms with the Apple and GNOME Human Interface Guidelines.

Searchable download actions manager

It is possible to search the Download Actions manager by file extension or description.

Cookies can be searched by hostname/domain and cookie name, and are organized by hostname in a tree format instead of a flat list.


Firefox MSI package

The new MSI installation package facilitates distributed installation and provides greater flexibility to network administrators wanting to deploy Firefox in a corporate environment.

Support for profile "temp" directory on local filesystem

It is now possible to store the network cache (copies of visited webpages) and the XUL fastload cache (precompiled user interface code) on a local disk, while keeping the rest of the profile data on a network drive. This will increase performance and reduce network traffic for users in a network environment.


"Sanitize" privacy feature

The "Sanitize" feature provides an easy way to quickly remove browsing history, cookies, cache, saved form information, and other personal data. The items to be removed can be customized, and the feature can be activated using either a keyboard shortcut or through a menu item.

Image thumbnails as tab icons

When viewing images, tab icons now display thumbnails of the displayed image.

Fast back (and forward)

This very experimental feature allows much faster session history navigation. The feature is off by default but can be enabled for testing purposes by setting the browser.sessionhistory.max_viewers preference to a nonzero number.

Anonymous FTP login failure behavior

FTP users are now prompted to input a name and password if anonymous access fails.

CSS at-rule for matching on site/document URL

The new @-moz-document rule gives users the ability to match page objects per-site, using CSS. This makes it possible to include site-specific rules in user style sheets (userContent.css). David Baron's post to www-style explains how the rule can be used.