SAN FRANCISCO--The next generation of Internet Explorer is nearly ready for the public at large, as Microsoft announces the release candidate of Internet Explorer 9 at the Hang Art Gallery in San Francisco's Union Square this morning.

A massive list of improvements debuted in the new RC, available for 32-bit Windows 7; 64-bit Windows 7; 32-bit Windows Vista; and 64-bit Windows Vista. Among the most notable enhancements are the new ActiveX filter, expanded support for HTML5 and "future-tech" standards, and advertiser tracking protection, which also was introduced this week into a prerelease version of Firefox 4.

The feature changes from the first beta are focused largely, yet not exclusively, on security. Like the Firefox 4 feature, the new "do not track" feature will prevent Web advertisers from tracking your behavior using a header-based solution. Unlike Mozilla's implementation of the protection, IE9 uses both the header and customizable blacklists, Internet Explorer business and marketing senior director Ryan Gavin said in an interview yesterday. "Using only the header is too narrow a solution," he said, noting that Internet Explorer also allows users to create a whitelist for sites that people actively want to track online surfing behavior.

If you go to the Gear menu and then the Safety submenu, there's an option for tracking protection. Clicking it opens the Manage Add-ons window and defaults to the new Tracking Protection tab, from which you can add sites that you want to block. Once the feature has been enabled, simply start browsing. If you go back to the list after checking out a few sites, you ought to see that the list has auto-populated. The configurable number below the main list allows you to set your tolerance for being tracked. If you set it to three, for example, the tracking protection will wait until it sees a tracker on three or more sites before blocking it.

(Credit: Screenshot by Seth Rosenblatt/CNET)

Also new is an ActiveX filter, which you can use to block all ActiveX content and then selectively activate it on a per-site basis. For people unfamiliar with why ActiveX technology is potentially dangerous, to function it requires full access to the operating system that the browser is running in. The new ActiveX filter gives you the ability to restrict ActiveX on a per-site basis, with a toggle in the location bar. If you go to the Gear menu and then the Safety sub-menu, you can block all ActiveX content with one click. Then on the right-side of the location bar, click the circle with a line through it to allow ActiveX content to load on a per-site basis.

Performance gains have been dramatic in the IE9 beta with Microsoft's new JavaScript engine Chakra, and the release candidate continues that trajectory. IE9 RC now places right in the same ballpark for speed as Firefox, Chrome, Safari, and Opera, its four primary competitors. And according to Microsoft, IE9 actually placed fastest on WebKit's SunSpider test.

Also new in the release candidate is expanded support for HTML5 and other "future-Web" technologies. These include support for the geolocation feature, HTML5 semantic tags, CSS3 2D transforms, and support for the WebM video codec. These features are largely present in other browsers, so that they're finally coming to Internet Explorer must be a comfort to developers.

(Credit: Microsoft)

Quite a few minor improvements have been made since the last beta was released, too. The default maximum temporary Internet file size has been increased to 250MB from 50MB, which means that while your cache will be significantly bigger on disk, IE can store more data locally and make it that much quicker to load Web content. Pinned sites have been extended to the trackless private browsing, and you can now set tabs to show on a row below the location bar, which gives them the width of the browser to be displayed. Background tabs have received a Close button, which appears on mouse-over, and Microsoft has tweaked the interface itself to cede more space back to the Web page being displayed. In other words, IE9 RC is thinner than IE9 beta.

While testing the release candidate yesterday, I was pleased to discover that the instability that had plagued the first beta was gone. The release candidate didn't crash once over a six-hour period of use, although it did hang for a few seconds several times. Sites loaded quickly, and most importantly the browser not only felt ready for daily use, but felt like it could stand comfortably next to other modern browsers.