The second "platform preview" of Internet Explorer 10 was made available to developers last night in a series of blogs, community alerts, and privately held briefings.
With this update, Microsoft says that IE10 continues to deliver support for site-ready HTML5 technologies, as well as improving performance through support for several new technologies like CSS3 Positioned Floats, HTML5 Drag-drop, File Reader API, Media Query Listeners, and initial support for HTML5 Forms.
According to Microsoft, "HTML5 application performance improves across the board, as well as the ability to deliver better performance with more efficient use of battery life with new technologies like Web Workers with Channel Messaging, Async script support, and others."
Web application security is said to have been improved, using the same markup with support for HTML5 Sandbox and iframe isolation. Microsoft is keen to highlight IE10's continuation of IE9's precedent for enabling web applications to do more in the browser without plug-ins.
This IE10 platform preview includes parsing improvements from the W3C HTML5 spec, reflecting the fact that developers can now expect the same behavior in all compliant browsers, even for imperfect or invalid markup. Speaking directly to Microsoft's Ryan Gavin, senior director of Internet Explorer business and marketing, and Rob Mauceri, partner group program manager for Internet Explorer, DDJ online learned that Microsoft has played a very active role up on more than one W3C working groups.
One can only hope that Microsoft's proximity to working groups and new specs as they are laid down will result in maximum interoperability as the product evolves.
With platform previews, Microsoft states that developers can try out new technologies and provide feedback without any confusion about which technologies are site-ready and which are experimental. This approach is hoped to enable the technical community to work through safety issues before putting any consumers at risk — it also minimizes wasted effort rewriting consumer-facing sites.
HTML5 is the first version of HTML to define the behavior of invalid markup. Rather than relying on "fix-up" rules that vary from browser to browser, HTML5 parsing behavior is now specified in a way that developers can count on it.
IE10 now supports the File Reader API and HTML5 Forms validation, as well as advanced hit testing for more complex selection scenarios like graphics editors, games, and other applications that typically use multiple graphics layers.
Looking ahead, Microsoft's IE blog team states that, "As different browsers support developers using the same markup to achieve the same results with great performance, we can all realize the promise of HTML5 applications. To this end, we have posted over 270 new tests to the IE Test Center and submitted them to the standards bodies."