For some reason, Microsoft Internet Explorer installs over any previous or later versions of itself, so it is difficult to test your page on Internet Explorer 3, 4, and 5 in quick succession. There are several ways to work around this limitation that don’t require one machine per version of Internet Explorer.
Some people set up multiple hard disk partitions, each with a different instance of Windows in order to install several versions of Internet Explorer on the same machine. Level 2 or higher members of Microsoft’s Site Builder Network can use a free service called browser snapshot which provides images of a submitted URL as the page would appear on Internet Explorer 3, 4, and 5 (as well as various versions of Netscape). Lastly you can install the 16-bit version of Internet Explorer 3 side-by-side with the 32-bit version of Internet Explorer 4. The primary caveat with the 16-bit Internet Explorer is that it doesn’t provide exactly the same functionality as the 32-bit version in some areas, such as Java.