Internet Explorer 11 Developer Preview is an early look at the next incarnation of Microsoft's browser.
New or enhanced support for a host of web standards will help to extend the browser's capabilities. WebGL can create interactive 2D and 3D environments, for instance; Media Source Extensions (MSE) allows IE to automatically switch video bitrates depending on network conditions, delivering smoother playback (although only on Windows 8.1 at the moment); the browser can now download video without caching it to disk, extending battery life; and support for the HTML Full Screen API means videos can now fill the screen.
Elsewhere, extended support for more HTML5 and CSS properties will make web pages look better than ever; the developer tools have been redesigned; and there are various other smaller fixes and tweaks (Microsoft says IE11 "includes extensive improvements to the built-in text editor", for instance, although we're not sure exactly what they are).
Please note, the main downloads are available for Windows 7 and Server 2008 only. If you're running Windows 8, it's assumed that you'll obtain the browser by upgrading to Windows 8.1.
If this is inconvenient, though - or you're worried about installing such an early preview (and you should be, it could contain major bugs) - then you can alternatively download virtual machines with a range of test environments. There's variously support for VirtualBox, Virtual PC, Hyper-V and VMWare Player, on Windows, Linux or Mac. Microsoft's modern.ie site has more.