Inside Firefox 3.5 – what’s new for developers

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From the new features comes new things for developers to play around and enjoy in the new version of Firefox 3.5, and because of this, will now bring you up to speed what developers can now use in the latest version of the open source browser.


While the <header> and <footer> blocks are not known to be supported yet, the <video> and <audio> tags are now supported, allowing developers to add and embed audio and video formats to HTML documents without the need of Flash.

However, this is limited to Ogg Theora, Ogg Vorbis and WAV formats, but we are expecting that this should increase as HTML5 support continues. Also supported is the drag and drop API in HTML5, the use of the HTML 5 offline resource specifications, and the canvas elements – including shadow effects.


The Gecko engine, which renders the page you are visiting for Firefox, adds the support of CSS media queries, allowing the same CSS to be used, but inside there are specific areas that are rendered for print, screen and/or projectors. Also the :before and :after pseudo-elements have been updated to meet CSS 2.1 specifications, and support for “ch” to be used as a unit of length.

For CSS3, the new @font-face rule is supported, so sites with fonts that are not in the user’s computer can be used on the site, without the need of having the font – eliminating the use of sIFR and image text replacement. “opacity”, “text-shadow” and “word-wrap” are also now supported.

For Mozilla CSS extensions, the –moz-opacity has been dropped for the opacity property, while new extensions have been added.

SVG and Other

What’s new in this browser as well is that it can support SVG filters and effects to HTML and XHTML content, and colour correction based on the ICC standard. Also included is MathML, the Animated Portable Network Graphics format (APNG), new support for microformats and native JSON.

Firefox’s DOM features have also increased, with support for the “localStorage” property, web workers, mouse gestures, geolocation and locating DOM elements using selectors. Javascript has also been upgraded to version 1.8.1, and there is now support for HTTP Requests to be made cross-site.