NN 2, IE 3
You want to test a page on as many browser brands, versions, and operating systems as you can to verify compatibility, but some browsers don't allow multiple versions to be installed or run on one computer at the same time.
The commercial software program called Virtual PC by Connectix Corporation (http://www.connectix.com) allows you to create multiple instances of a Windows computer on a single computer. Each instance runs inside its own window and does not conflict with other instances. If you are a Windows-only user, this means that you can create and run virtual computers for different Windows and Internet Explorer versions. On a Macintosh, you can have the same multiple-PC setup, as well as your regular Mac OS running at the same time (see Figure 5-1). Since both the virtual Windows machines and Mac can share common folders, you can edit an HTML file where you like, and load the same file into many browsers and versions at once.
As yet there is no Macintosh emulator for Wintel hardware, so Virtual PC running on the Mac is a more versatile environment than on the PC. Both are capable of creating Wintel-based instances of Linux, and both have had the x86 version of Solaris 8 install successfully (although it is officially supported only on Virtual PC for Windows).
To help you keep all the browser and OS versions straight, you can create Windows instances that are essentially snapshots of history. For example, one virtual machine can be running Windows 95, Internet Explorer 3, and both Netscape 2 and 3; another instance might have IE 4 and NN 4 running under Windows 95; another instance might have the same browsers, but under Windows 98. You can even add Opera browser versions to appropriate virtual machines (e.g., Opera 6 with IE 6 and Netscape 6).