The Internet Explorer Platform Preview 4 is a very basic browser that demonstrates some of the technologies that we'll see in Internet Explorer 9.

There's the new script engine, for instance, code-named Chakra. This compiles JavaScript in one CPU core, while the rest of the browser runs on the other, delivering a massive speed increase that sees the preview outperforming Firefox.

Microsoft have been working to improve IE8's woeful standards support, too. While there's a long way to go, the preview shows real gains in HTML5, DOM and CSS support (its Acid3 score is now up to 55), which means you'll see more sites as their designer intended.

And new support for hardware-accelerated graphics, in the form of DirectX 2D, ensures performance improvements across the board.

Don't expect to do much with the preview, though. It's very limited at the moment, with no toolbar, no security, not even a Back button, and is really just a basic demo aimed at developers.  It is safe to install, though, and won't affect your existing IE setup.

Please note: Windows Vista owners must have DirectX 2D installed before they can install the Internet Explorer Platform Preview. If the setup program complains that this is missing, then go to Control Panel, open Windows Update, check any optional updates you have available, then find and install the Platform Update for Windows Vista.