At the present moment, I have three virtual machines that I use to test website rendering on different browers. Not only is the process tedious, it is time-consuming and not interesting. Microsoft heard my (and many other web developers out there) prayers and answered with Expression Web 3 with SuperPreview.
Expression Web SuperPreview for Windows Internet Explorer is a stand-alone visual debugging tool that makes it faster and easier to migrate your sites from IE6 to IE7 or IE8. With SuperPreview, you can ensure that your Web sites work correctly in IE8 while also maintaining compatibility with earlier versions of IE.
Expression Web SuperPreview lets you view your web page side by side in multiple browsers, including multiple versions of IE. For example, you can see your page in IE8 and IE6 simultaneously. There is also an onion-skin overlay view which let you view the different versions in layers highlighting the differences in rendering as well as the problem elements.
I tried Expression Web 2 but did not like it very much because it had very little to offer above what Visual Web Developer already did. Hence I settled for Visual Web Developer when I need to whip up a quick web app. With the new version of Expression Web, I may have a reason to keep it installed on my computer.
Expression Web 3.0 can be obtained here.