Have you ever wanted to login to a website using the same browser, but with multiple different sessions. For example, log in to GMail, using Google Chrome, but as two different users. Normally, the moment you login as the second user you will be logged out from the first session because the session information [cookie] is “shared” between the browser windows.
Here is a simple trick. Create a new short-cut to Chrome and add “–user-data-dir=c:\temp\user2” to the Chrome command and you’ll get a second “instance” of chrome, with completely different session information. If you want another instance, use a different directory name, etc. As a new instance it will not have any of the settings from your “normal” instance but it’s great for testing websites.
BTW… unless you want to use the same browser information in the future, don’t forget to remove c:\temp\user2 when your done.