HTML 5 Support
However, a much more significant new feature in Firefox 3.5 is its extensive support for HTML 5. Although it is not yet a full World Wide Web Consortium standard, HTML 5 is already offering an intriguing glimpse into the future of the Web. Indeed, HTML 5 is much more than just the next version of HTML; it is a reimagining of the Web and how browsers work, providing many of the same powerful GUI interactions that one gets from RIA (rich Internet application) platforms or even desktop applications.
One of the more interesting aspects of Firefox 3.5's support for HTML 5 is in its handling of video. Throughout the history of the Web, browsers have treated video as a second-class citizen, relying on plug-ins and other applications to handle video. However, through its implementation of HTML 5, Firefox 3.5 can handle video directly, in the same way that the browser can display images or text.
This means much more than just the ability to play video in a Web page. With this implementation, video can be integrated with other Web content in ways that are much more difficult to do using traditional methods. Video can react immediately to actions performed within the Web page, and Web content can be changed in response to things that happen within the videos. There are many interesting demos available on the Web showing the power of this integration, and I think they are just scratching the surface of what HTML 5 will enable.
While this is one of the most intriguing new capabilities of Firefox 3.5, it is not an edge the browser will hold for long.
Safari and Opera have also taken strides to support HTML 5, and other browsers will also soon follow. Of course, in the end, anything that increases the power of the Web and browsers is probably a good thing for Mozilla.
Along with the HTML 5 support, Firefox 3.5 has also boosted standards support in general. In the Web Standards Project's Acid3 test, Firefox 3.5 shows considerable improvement over previous versions and does well, though it is still behind Chrome, Opera and Safari (though well ahead of IE 8).