Expression Web SuperPreview lets you view your website in IE6, IE7, IE8 and any other web browser you have installed, and switch between them as you please. That means you can switch between viewing your website in Shiretoko (Firefox 3.5 beta), Internet Explorer 6, and the Safari 4 beta with the click of an icon. You can even compare them side by side. Perhaps the coolest feature is that you can overlay the different renderings on top of each other in an onion-skin mode, allowing you to fully appreciate the Cuil-like approach IE6 takes to rendering webpages.

SuperPreview also includes a CSS inspector, DOM inspector, rulers, guides, and other such functionality we’ve come to love from Firebug and other great Firefox web development plugins.

For the time being, SuperPreview is released as a free (as in beer) beta, which you can download from here (250 MB). It will eventually be part of Expression Web 3, which probably means it will not remain free, so make sure to get the beta now.

For more information, check out the original MSDN Post, and this fantastic writeup from istartedsomething.com.

H/T: HackerNews