One of the sites there was an interesting project, involving a complete emulation of Windows 98 in a web browser. The system, by default, runs in a small window, however with the appropriate shortcuts you can increase it or use it in full screen mode. It works on the principle of virtualization, so it takes some time before the screen will display the appropriate options and actions entered by the user.
Windows 98 in a browser just shows how quickly technology is advancing, which allows you to create extensive applications that require only Internet connection. It is worth remembering, as before looked operating system from Microsoft.