If you have been developing with Windows Identity Foundation at all using Claims-aware Web Sites and a Security Token Service, you may have realized some of the frustrations with developing using Internet Explorer.
The way in which Claims-aware applications work in conjunction with an STS, is that the token information is stored in a cookie on your browser.
Well, if you are testing tokens from multiple users to see how they render differently, as you can probably guess, this becomes a bit of a problem. Since the cookies are stored locally on your browser, even when you close the window, the cookie is not deleted from your machine. Therefore, the next time you attempt to log into the system, you are automatically re-directed because the cookie is still present.
Unfortunately, unlike Mozilla Firefox or Google Chrome, there is no easy way to manage these cookies and remove individual cookies. Even using the new Developer Tools available with IE 8 does not provide this capability.
But, if you are using Firefox or Chrome, you can simply use the option to Remove Individual Cookies. Using this capability, you can simply delete the cookies (from localhost or elsewhere) that were placed on your machine. Once the identification information has been removed from the browser, you can now log in as an alternative user.
Below is a screenshot from the Cookie Manager present in Firefox. You can find this tool under Tools-->Options-->Privacy-->remove individual cookies (hyperlink)