When you are developing web sites, one of the hardest things to deal with is the multiple versions of Internet Explorer that are in wide spread use, mainly IE6 and IE7. There are some web sites that can help with this - they'll go to your site in various versions of the browser, render the page and capture a screen shot for you to see. While this is helpful, it only goes so far: you can't see this until you publish your page so their is no capability to do iterative development or troubleshoot problems; and you can't see how dynamic effects, like those done using javascript, work in the various browsers.

One solution is the use of virtual machines. You set up VMs, each with a different version of the browser. While this is the most reliable and full-proof way to do the testing, it requires expensive software and it takes a long time to set up all the machines.

A less perfect but far easier, and cheaper, solution is to try using IETester. IETester is web browser built using the IE engine that can switch between different versions of the rendering and javascript engines within the browser itself. This lets you test the various flavors of IE in one browser quickly and easily. It's still an alpha release, so there are some issues. But using this can make your development cycles a lot quicker if you don't have VMs set up.