Today, the IE9 development team
announced the release of a new version of the IE9 Platform Preview.

You can download it here
ie.microsoft.com/testdrive (version number 9.0.7916.6000).
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Let me remind you that the Platform Preview is a special version designed for developers. It contains only the rendering engine and the javascript engine (+ developer tools) and does not contain the traditional UI browser.
After the release of IE9 PP4, the next in line is the beta version.
What's new in IE9 PP4?
In short, an increase in speed, improved standards support, bug fixes and new tests and examples.
Javascript
Essentially, no significant changes took place in the JavaScript engine (Chakra) itself; nevertheless, one fundamental shift does take place.
In the new version, the JS engine is integrated with the browser, which makes it possible to remove intermediate information transfer and coordination of two DOM in one application.

In fact, IE9 was the first browser in which the browser and the script engine have a common DOM based on ECMAScript5. In other words, now all DOM objects are full ES5 objects. DOM binding is based on the
WebIDL W3C standard.
Be sure
to check your browser for DOM and ES5 support .


And, of course, all this could not affect the performance:

Standards Support Tests
New tests for standards support
The collection of test examples in the
IE Testing Center has been replenished with 519 new tests, the total number has grown to 2138.

Let me remind you that all tests are open and are being developed in collaboration with the W3C working groups. Feedback on tests of W3C standards can be sent to the appropriate working groups, and on support for ES5 in IE9 - to
Microsoft Connect .
ACID3
With all the ambiguity of ACID3 as a set of tests to test support for standards, the new result is good news;)

Unsuccessful tests:
- Test 75 failed: Object doesn't support this property or method
- Test 76 failed: expected '0' but got '100' - Incorrect animVal value after svg animation.
- Test 77 failed: Not implemented
- Test 78 failed: expected '90' but got '1.9237771034240722' - getRotationOfChar (0) failed.
- Test 79 failed: Not implemented
Missing points relate to support for SVG Fonts and SMIL Animations. Detailed comments on this subject can be
found in the IE team blog . In short, we are talking about the fact that now in working groups they note weak support of both directions, there are some contradictions that are actively discussed in the context of integration with Web Open Font Format (WOFF) and CSS3.
New Demonstrations
Together with the new versions of IE9PP4, new demo examples have appeared
on the project site , showing both working with HTML5, DOM and E5, and support for SVG and Canvas.

Try to play
Hamster Dance Revolution , create a musical composition in
IE Beatz

And do not forget
to check your browser for psychedelic ;)
Additional Information
On Channel 9, 4 demo examples for IE9 PP4 became available, revealing specific technical details:
You can see the release notes for IE9PP4 here
ie ie.microsoft.com/testdrive/info/ReleaseNotesWhere to write about errors?
If you find a bug in IE9, be sure to write about it at
connect.microsoft.com/ie - this will greatly facilitate the life of web developers in the future;)
ps
Bagu eval ('- 1') with fixed. No wonder we all reportable about her;
pps Get ready for the beta;)